>>I know that an amp is an amp and there shouldn't be any difference in sound quality, but for some unknown reason I preferred certain genre's of music on the Yamaha more. Classical and jazz just seemed to be more 'right' with the Yamaha.
That is also the perception I picked up over the years. I try not to think about it because (a) I never did any A/B testing and (b) the speakers were different as well (Yammie speakers on the Yammie receiver).
One day somebody here should actually pile up a few receivers and compare them directly. Until then, every time I see the Yamaha "look" on a receiver I think of crisp, clear jazz