Of those mentioned, I would say the Arcam (I have only heard the 300, not the 350 unfortunately). FYI, I ended up with the B&K 507 which I liked best. The B&K excelled in stereo over the Arcam IMHO, but the Arcam was also very good.
HT more of a push between these two.
Did not listen to the NAD for this purchase, but from a cost/reward basis, NAD is fine. Did listen to the Rotel, having owned in the past. Just don't have the same confidence level in the Rotel as the Arcam and the B&K.
For this amount of money (Arcam 300/350) you should listen to the B&K. I can't begin to tell you how happy I am with mine and just as much with the company itself.
ckoffend