Naim Hi-Line on my equivalent setup. SL DIN IC is a nice improvement over the Hi-Line, adds a little space and brightness, not for everyones ears though and better matched with a NAC ideally.
WitchHat are worth a look in terms of price/performance.
I’m not sure where in the world you’re based but Hi-Lines circulate used fairly often typically around 50% of retail price for a new one. Older ones have more “fragile” connectors, they changed the plastic type/formulation and more recent ones are a little more robust. If you look for a used one, if it’s in a metal tin or has packaging with a Green Naim logo it’s older. The newer ones are in a cardboard box with a Black Naim Logo.
Naim will repair them FoC via a dealer as required.
Chord Company DIN cables usually work well, the ARAY based ones I found better in general.
I also use the TQB did-din which I much prefer to the HiLine between NDX2/XPSDR & 252. Mine picked up s/h for around £250.
G
Yes, as Chris , points out, you need to try at home, SL or any other. My recommendation is Naim std cables or a lot of leg work yourself. I ended up with Witch hat Morgana but, that’s my personal choice. I found cables more difficult than black boxes to find an improvement.
It’s all about the black boxes! In my opinion matching the wires up is about eking every last drop of performance out of those black boxes before you look at a further upgrade.
I’m based in Belfast so a home trial of a SL is out and even if I could, I’d be terrified I might like what I hear so possibly for the best! Peoples opinions seem to vary on both the SL and the HL but I’ve yet to hear anyone have anything negative about the Morgana - the return option sealed the deal.
Will post some feedback once it arrives and has had some time to bed in. Thanks for everyone’s valued input - much appreciated 
I picked up a used Hi-Line to replace the standard interconnect and it was a lovely subtle enhancement. The dealer I purchased it from let me demo it for a couple of months. (I did pick it up right before the covid stay at home period so there was no rush on making a decision.)
See if your dealer has a demo laying around…
Good Luck!
Yes, i bought Morgana…hope they work for you, best of luck.
It’s an interesting one. For me going to a SL din-din from a HiLine was as big as adding a black box when I was using it into a Supernait2.
First and only time my wife sat up and asked what had I just done.
My dealer gave me mine as a courtesy.
Do you reckon your Hi-Line was maybe not optimal? I have sent mine off for repair twice and the second time it came back, it sounding quite a bit better than from when it was new, and also from the first time it was sent off for repair. The second time round Naim replaced both the connectors and the whole cable just feels mechanically looser yet more robust at the same time. Sounds fantastic!
I had a Hiline once, between a CDS3 and 552. I was never convinced it made much of a difference despite optimal installation. Then one of the ends spontaneously self-destructed. So I shoved it back together, boxed it up and sold it.
Yes. I mean’t ‘optimal’ as in not being built right to begin with. After sending mine off twice and hearing it extensively, after living with it for five years, i’m convinced that was the case with mine…
Now it just works regardless of how it is installed. I just plug it in like any other normal interconnect. Sounds fabulous and quite a bit nicer than the grey/lavender cable…and doesn’t break anymore!
No, the HiLine is what opened my eyes to make me take cables seriously and then soon turned into the SL.
HiLine is fantastic.
Interesting. Thanks.
At the moment I am using a hi line interconnect.
I have also had great success using a custom built silver interconnect from Yannis Tome, very very good value for money.
It can happen without any physical contact, like the stuff of magic…
When I upgraded from the standard Lavender to a HiLine, I experienced it as a good and worthwhile upgrade. Most recently I bought a secondhand SuperLumina. I did not experience a big upgrade there, and experince the sound on par as with the HiLine
By the way: I read great experiences with a Morgana which is reasonably priced and worth considering for the OP
Iver
Chord Signature is definitely worth a try!
I’m very happy with Morgana interconnect on my NDX2/SN3.
I have a NDX/XPSDR as opposed to a NDX2 and couldn’t get on with a Hi-Line so tried a TQ Black, which I then bought.
More balanced and cohesive than the Hi-Line, IMO.
Mind you, I’d love to hear what a SL could do!
I use an AR Sound Lunar from NDX2 to SN2. Liked it so much I’m going to try the Lunar Equilateral.