Amp recommendation for RS6

You won't hear a big cable difference. Chord makes the naim cables. For the most part, I use Audioquest. They work well with just about anything as long as you stick with copper. At the time, I did an AB with the Jaguar and Cheetah using my Arcam 33 with the naim. I honestly could not hear any difference whatsoever between the two. I usually hear a big difference between them so I would not overspend. I can say, though, that I brought my CD player into my naim dealer to for a demo and I brought my AQ cables with me because I know them well, and the dealer was blown away by them. On the higher end naim gear, we did get some very good results. The dealer told me he was going to pick up the AQ line.

Tested RS6 with Naim Nait 5i and Audio Analogue Puccini SE.
Both amps acted very well but even the Naim was a little bit fatiguing in this combination,it brought much more openness,bass control,separation to RS6.
AA had a little bit more warmth ,the voices had much more body than Naim but the bass was somehow muddy and uncontrolled.Also lacked the dynamics needed to modern genres and rock.

I will also give another chance to NAD C355.If doesn`t work I will definitely go for Naim.

I used a CJ mf2250 with Silver 5i's...was an excellent combo.

These are very good speakers with tube amps.
Something like the Ming Da EL34A/B would be great.These are superb sounding tube amps and an absolute bargain.Also great build quality,very quiet and have none of the soggy bass or lack of drive you find in lesser tube amps.
I do not think any mid priced SS amp would come close.

i'd also opt for tubes with the rs6, which can sound very forward and bright--perhaps something like the vincent hybrid or jolida would tame 'em.