I used Topaz and it provides lots of body for the music. Its treble is not its strong point, IMHO, but it sounds rather smooth and I'm more than fine with it. I'm OK with all sort of music with this cable.
You may not

it though. What's your source anyway?
I think you should try AVBestbuy's Firebird I talked about it elsewhere on this webboard. Much less body, less smooth but lots of detail with tighter but much less bass body vs. Topaz. You may

lots of detail and nuances of the sound it gives out. Though it didin't match with my set, I think you can try it with minimal cost. According to their website, their silver cables have even more tighter bass with more emphasis on mid and treble. You can also try it too and, to me, that's the best way to tell whether it really solved your problem.
Though I don't know your source, come to think about it, I'm a bit worried about what you said as it seemed NAD and NHT seem to go together quite well in general. I'm afraid you don't

the style of this set and this will be very problematic in trying to fix it.