Naim Nait Integrateds... Sound Quality Comparison, User Comments and Bang for the Buck

Have been considering a Naim Nait integrated. In doing so, I’d like to ask what for the user-lowdown on the following models when comparing to each other based on sound quality, characteristics and price. Everything I am considering is used. The reason I am not including the 5i (non-italic) is that I have owned this model in the past. I liked the sound a lot, but my only criticism is that I felt is lacked low bass response and punch. However, the dynamics were there, as well as the smooth, full mids that would not strain or get harsh when driven. Treble was neither bright nor veiled—just right. From my readings, it appears that the lack of bass concern was corrected on the 5i-2 model and onward? I’m planning on possibly getting a CD5x to mate with one of these Naits. My music flavors are pop/rock/prog (i.e. David Bowie, old-Def Leppard, Pink Floyd) and electronic (i.e. Tangerine Dream, Kraftwerk).

Here are the models I am considering:

5i-2 (non-italic)

5si

XS

XS-2

For those who have owned all four model at one time or another, and/or, were able to compare any of these models at the same time, what are your comments on each regarding sound characteristics? Do they all have the basic foundation of the “Naim Sound?” Are there some that are punchy in bass vs others? Some that are brighter in the highs? Any more laidback in the mids than the others?

As for used pricing (according to ebay sales history) it appears the 5i-2’s are selling for an average of $575 shipped/paypal. The XS’s are averaging $975 shipped/paypal. I could not find much if any sales history of the 5si, but would assume around $775-$800 based on the other figures. XS-2’s appear to be listed on the used pages for around $2,000 used, but I wonder if any can be had for $1,500 shipped/papal or less? What’s interesting is that all the ebay sales pricing is before the 10% final value fee.  

As for sound for bang-for-the-buck, if a 5i-2 can be had for say $575-$650, it is worth another $200-$300 or so, to go to a 5si? Or, is it worth another $425 to get an XS? As for the XS, let’s say one can be had for $1,150. Is it worth another $600-$800 to get an XS-2? As for my specs, my room is 12x12 and using Vandy 2c’s. Cables are AQ CV-4 speaker cable and Mogami 2549 interconnects. I’ve read on another post that AQ sounds very nice with Naim’s current gear. When I had the 5i (non-italic), I tried the NACA5 cables, but didn’t like them. I felt the sound was dull. The DH Labs Q-10 I had at the time were much better, but were a little bright—since they are silver-coated copper. After that, I had sold the 5i at the time and moved on to other gear.