Got a Supernait 3 with a Hicap DR and an Auralic Altair G1. I also use Roon with a Nucleus as core. I am now thinking about upgrading the streamer. What would be the most appropriate upgrade: an NDX 2 or an Auralic Altair G2.1 or a Vega G2.1.
I mainly stream music from Qobuz, with about 50 albums on an SSD in the Nucleus.
Music genres range from pop, rock, jazz to classical.
Not just because I own one, but I would say NDX2. Of the choices you list, it is the one that duplicates the functions of your SN3 the least. In theory, this means more of its “goodness” is in the important bits - the streamer and the DAC - with no effort wasted on redundant analog inputs and/or volume controls.
Andrew
It depends on source you are playing. I use Amazon HD and the Auralic suits me because of that. It also has a very good sound. I haven’t heard the ndx2 against the Auralic so you need to find a demo and listen. Purely in terms of upgrading from your Altair G1, the logical upgrade is the Altair G2.1. I am not sure the SN3 will show the advantages of the Vega G2.1, you need to find a dealer that can demo one. I have gone a slightly different path with streaming as my preferred main source and have the Aries G1 plus the Vega G2.1. I will upgrade the Aries with a G2.1 when I can locate an ex demo.
The NDX2 will give you a visual match, and the convenience of System Automation volume control from within the Naim app. Beyond that, you need to listen and decide for yourself.
The NDX2 and the SN3 are among the favourites here, for a good reason. I’ve had the NDX2 and have done the comparison you are asking about. To my ears the NDX2 DAC sounds richer and sweeter than Auralic’s Vega G2 DAC, which in turn is more detailed, transparent/spacious and with better soundstage. I found the higher end (G2) Auralic DAC + Naim amplification to make for a rather good combination. If you are not so sure that you like the Altair G1’s presentation overall (which G2’s DAC would definitely improve further as above), then probably good to try the NDX2? Depending on your speakers you may also prefer one to the other?
I have an Altair G2.1, it is very good indeed. Did the comparison with the G1 and the NDX2 and liked the 2.1 best. Easy to use, well built, sensible range of features and great sound. Your opinion may vary, but go and hear them.
I listened to the Auralic Vega G2.1 v the NDX2 extensively. I formed the opinion that the Auralic is better in all ways - until you add (in my case) and XPSDR to the NDX2. Quite a different budget though, especially now. Interestingly I also know a couple of local folk using the Vega straight in to a 250DR with great results.
The Altair of course is wireless, the Vega has to be wired to an ap.
I run a Vega G1 on its own in to a 250. It is excellent but the Aries plus Vega G2.1 is a marked improvement.
Functionally these are somewhat different in that the NDX2 is of course a streamer/DAC which is intended to be used with a preamp or integrated amp whereas both Auralics have a rather good (to my ears) Class A output module and resistor ladder volume control. Between the two Auralics, the Vega has better SQ but offers somewhat less functionality (no built-in server, for example). However, Roon will likely take care of that.
As others have said, auditioning is strongly recommended and if you can and do audition, I’d suggest trying the Auralics straight into a power amp.
Roger
I was considering the same question myself. I plan to upgrade essentially my entire system by the end of the year. I considered the NDX2 but am now leaning strongly to the Aires 2.1 for several reasons: First, the Aires 2.1 appears to be about the best streamer out there by all accounts. It also has the ability to take an SSD and so replicates the functionality of my Core. It can also take a SuperDrive as an input (I happen to have one) and rip CDs to its storage and/or play them. So further replaces some Core functionality, not to mention my CD player.
There is also what it doesn’t have: no DAC. I don’t really want a DAC included in the streamer. DACs in the last year or so seem to have been getting better and better, and getting less expensive at the same time. There are some amazing products out now from companies like Topping that out-perform everything else. My local dealer does not carry Topping, but showed me some other (also Chinese) products when I was in yesterday. They were very good and looked and felt much more expensive than they were. I don’t know how the DAC in the NDX2 performs, but I want to leave my options open.
The final reason, I’m sorry to say, is that Naim is not really price competitive in Canada. The NDX2 is almost $13K CAD. Far more than the Auralic offerings. Different if you are in the UK I expect.
Topping outperforms everything else. Normal, it’s a top-dac.
I may go for a Aries and Vega G2.1 if i win the lottery the second time 
And use the Altair G1 in the second system with the chrome bumpers
I think purchasers of £20k+ DACs from the likes of dCS might be surprised by that. Seriously, if that’s the range of DACs you’re looking at, an Aries G2.1 is likely to be a waste. I doubt you’d hear much difference between the Aries G2.1 and the much cheaper Aries G1 which also has all the features you’re after. The more expensive model is really designed to be used with Auralic’s Vega G2.1. Auralic use a special cable (Lightning Link) to connect them and they then function effectively as a single unit. I think your budget would be better spent on a more even share of funds between streamer and DAC.
Roger
I believe in being very careful in assuming that because something costs more it must be better. I have not heard the dCS DAC or seen any bench test results. If you have bought one and like it I have no problems with that. However when it comes to high price DACs I notice that in recent testing by a well respected reviewer, the Chord DAVE and headphone amp was surpassed (in the DAC section) by the Vega G 2.1 which was in turn surpassed by the Topping D90SE. Which is why I made my comment. In fact even the Topping E30 DAC (at about $200) was measurably better than the Chord DAVE. In the amp section, the Chord DAVE did not measure as well as the Topping A90 headphone amp (about $500). In listening tests, the A90 also out performed the DAVE driving high end headphones. I think the DAVE is about $14,000.
I’m all for people spending their money how they want, but if something inexpensive measures better than something of high cost, then what is the money buying?
I am sure that @Innocent_Bystander will agree with the post 13. A 200 dollars topping dac outperforms the Chord Dave. 
I haven’t heard so can’t comment. With digital, progress in technology means that better things can be possible at lower prices. A $200 DAC sounding better than Dave does seem unlikely, but who knows? I’d be horrified to discover such a cheap thing is as good if I had only just bought Dave, but that is not the case, and things move on…
It is almost cheap enough for me to take a punt and compare… Indeed I might look more into it because I have been wondering about sorting out a music system for campervan use (has to be headphone for decent quality due to space), and maybe if not as good as Dave for home use it might be good enough for that (and if as good or better I could get another and sell Dave before the bottom drops out of the market…)
Well I think that depends on what is being measured. I choose my kit by listening rather than how it measures, but I realise that auditioning is not always possible.
BTW I do not have and have never heard a dCS DAC (or Topping come to that).
Have fun choosing, but do audition if you possible can.
Roge
What was being measured was mainly noise and distortion, plus ability to drive demanding headphones. If the more expensive unit has greater noise and distortion and that is then heard in the listening tests (as it was), it is hard to argue that the unit that has this lower performance is better. Rather the reverse.
I agree that the final choice in buying something should be to listen to it, but I tend to look first for objective testing and eliminate components that do poorly overall. Then listen carefully to the units that did well, to pick one that indeed suits my needs.
Last week I bought a new set of headphones (hence my interest) this way. After reviewing test data, I listened to Focal Stellia and various Dan Clark pairs. They were all far better than the B&W PX7s I have, but I ended up choosing the Dan Clark Stealth. Couldn’t be happier! Now all I need is a better HP amp although my Atom (non-HP) does surprisingly well.
Well the 2 best DACs I have owned to my ears both measure badly as far as I know, Brinkmann Nuquist and PS audio PW DAC. But then I prefer vinyl so I must like distortion 
To each his own For myself, I stopped listening to vinyl (and tubes/valves) decades ago. I believe I am now cured 