I have the RX-750 (feel like I've said that a bunch lately) which is one of their cheaper models. I'm not sure what the difference in components between the higher and lower end stuff is (like heat dissapation and power creation, etc.), but I have never had a problem running a pair of M60s, QS8s a VP100 and some other small rear surround speakers fairly loud. Never had a clipping or overheating issue, never had a distortion issue. According to my wife, I like to listen to movies and music way too loud, if that helps...
In addition, my downstairs neighbor (not an afficionado at all) got a complete M2 system with a VP100 center. She bought an even less expensive Yamaha and also has had no problems.
I guess it depends on your room dimensions, and the volume at which you like to listen to music. Certainly, a cheaper model might, on average, last for fewer years than some other model, but in the short-term, I wouldn't worry so much about that (lemons aside).
The consolation, of course, is that if the receiver ain't cuttin' the mustard, it is an easy swap-out (unlike if you were suddenly and unreasonably dissatisfied with your speaker wire...).
Give a cheaper receiver a try. So long as the software decoders are good (which they all are these days), and the volume is sufficient, I think you'll be fine with a cheaper model. Heck, I don't use half the "bells and whistles" I paid for on my cheap model.
