Indeed Beachcomber’s suggestion would be worth doing before deciding. For your budget you could get the active version of one of their larger models, maximising bass response with guaranteed amp capability. As with my mention of PMC MB2 above, secondhand can help buy best.
All of course is subject to suitability in your room, and your taste in sound presentation.
Enjoyed my S400/Naca5 for more than 10 years. For me the speakers with great pace, punch and musicality. Plus excellent build, you do not see a lot in their price range.
Exchanged them with Kudos S20A/KS-1. The results have been truly stunning… Lost nothing from S400 qualities, but gained so much in transparency, stage, energy and… hi-fi.
I would guess they are entirely different in presentation.
The Naim speakers I have heard are nothing like Focals, which again have a varied presentation older or more recent editions.
As others say, a very personal choice.
Try the nicest Proac speakers that will work for your system and space. Be sure to get the ribbon tweeter. I don’t know your amp.
I would agree with Nigel’s advice.
I’ve just bought some 707 Titans and they are a brilliant speaker. However, my source is the ND555 and I would always upgrade the source first.
I used to own an NDX2 and the biggest upgrade to this source was an xps ps.
You have probably reached a stage in life called - audiophilic boredom …
You have a good system, but around there are noises and noises that- there may be something better somewhere …
And this idea digs inside you and makes you, stop enjoying what you have now.
There are two solutions to this problem-
Start a journey of testing, scanning and demonstrating other speakers that at the end of the day you will either purchase or understand that spending on replacement is not worth the difference between existing and new
2. Try to find an in-house solution in the form of a cross-examination of-
Dedicated line for system / quality power strip / improved power cable
Improved interconnects / improved speaker cables / improved stand
This will also save money, time and nerves …
good luck 
Excellent discussion going on and I really appreciate any of the comments so far. They indeed started a process to rethink my system in another way.
@ditton66 quality power strip, excellent interconnects/speaker cables as well as power lines are already in place.
I guess first thing will be to test, if a XPS DR on the NDX 2 brings a significant update over the currently used TP XPS. Later on I could try another pre-/power-amp combination. Nevertheless I always thought a 4k amp would be more than sufficient and drive any kind of speakers in an excellent way.
True to a point. But a 282/HCDR/200 or 250 will drive those same speakers even better.
That should be put to the test rather than assumed. I’ve certainly never heard any Audionet gear. If we’re just talking about drive then they do something called a Humbolt that appears to have plenty. The OP has already compared the supernait and found it wanting, as did I but that was the first version.
Personally I’d go source first with a 555ps as a first step, in fact I did when I had a CDX2 and tried one against an XPS2DR or a supercap DR on my 282, it stood me in good stead when the ND555 came out.
When I heard Ovator 400s, a little later, there was a traded in par of NBLs with passive crossovers on hand, the Ovators suffered somewhat in that comparison but the Ovators were brand new. The NBLs are still with me.
Gold.
Also gold.
I heard the K6 signatures… wonderfully musical. Enjoy!
The Audionet G2 is a 5300 euro amp and i understand that you prefer it to the senior Naim integrated so maybe a good idea would be to upgrade to the WATT model(12000 euro)and still you will remain with enough budget for very decent speakers and with a balanced system.Also in this way you will be able to avoid the naim multi box trap.
Funny that you mention the WATT. This was exactly what I was looking at today. I remember, why I opted for the Audionet initially: The Supernait hat a hum sound from the black box and a hiss in the tweeter. After considering a NAC/NAP setup I would end up with at least three black boxes and I find the NAC with all its inputs and rec-out options too much to just plug a NDX in. Nevertheless I will consider a home demo of the Naim combo and look further into the WATT option.
If you went for active speakers like the ATCs, you could sell your amp - but with the NDX2 you’d need a preamp. That could be a Naim pre, or IIRC ATC does a pre. However with only a digital source a passive pre might do - and might even possibly prove better. (I have no experience so can’t comment: my DAC has a fully variable output and is very stable driving a power amp direct, so I don’t use any preamp.)
(… which in those circumstances would REQUIRE a *cap PSU to work. Apologies if that’s stating the obvious)
I think what the experienced forum members are saying is that your end game speaker cost is at cost to an imbalance with your current amp- hence redirect money more toward the source argument. I went through a similar thought some years ago prior to multiple upgrades with Naim and what I did learn was that some speakers really are a game changer but once on that drug they too start to open up more upgrades - so thought bubble : End game speakers with non end game system isn’t right.
I would work backwards if I were you and ask whether you really want an end game speaker or a fantastic value improvement with the funds allowed. If it’s the latter I would spread the money between system and speaker.
Beefing up the NDX2 with a psu of choice, sell the current amp to add to the kitty, improve the amplification with Naim and then buy a pair of speakers that are not end game but are brilliant and different ( that’s important sometimes ). Try Spendor D7.2’s they are a terrific match …but when funds allow you can sell and upgrade - try classic 100’s but my point is I wouldn’t start at the 100’s.
I think the simple truth is being able to build on an ‘upgrade path’ with system satisfies our audiophile lust for years. good luck and let us all know your end game decision.
OK, source first then. I ordered a pre-loved XPS DR (18 months) from a Naim dealer to replace TP XPS. Furhtermore a Hi-Line DIN-RCA cable will augment the system. Looking forward to the delivery within the next days.
I used to own a Audionet G2 eons ago and I am very curious on how you find it better than a Supernait. When I owned it I regretted parts exchanging it with my then Accuphase E-405. To me though both of these amps are completely different sounding than Naim. Could you please elaborate on the sq differences
Regards
Lucifer
Well, the A-B-comparison was back in 2012, so I surely can‘t remember details. IIRC the Audionet was more clear in its presentation and had better treble resolution. I found two things with the Supernait 2 quite annoying: one channel was significantly louder than the other when I was driving the amp with low volume. Another point was a constant hiss from the tweeter. Both „problems“ were simply not there with Audionet. Furthermore I had a Naim DAC at this time, so there was no need for the D/A section of the supernait.
Ah so it was a Supernait 1. The 2 doesn’t have a built in dac. If you do try a more recent Supernait or nac/nap it will be interesting to hear what you think.
I just saw that you are trying an Xps and a hiline. Looking forward to hearing your findings with those. However, my experience with Naim amplification is that it is rather special. The Supernait 1 is not nearly as good as a 202/200 which in turn is not nearly as good as 282/250 and on it goes of course. 
Not to mention the amazing olive amplifiers. They sound like nothing else. 