I'm up to spend big bucks for audio (almost all my money) but god damn these receivers can be hard on the bank account!

Ok...so now, after a terribly long year of reading reviews, I finally choose Onkyo as a receiver manifacturer since I laughed at pioneer and yamaha hasn't clear enough sound. But the poblem is... when do I stop?! How am I supposed to know which model suits for me? And is there really THAT of a difference of quality and power between those? Here I'm talking about TXSR-XXX series:

TXSR-503
TXSR-602
TXSR-603 or the big mofo,
TXSR-701

(I LOVE the look of the two last though )

I'm planning to keep this piece of equipment for about 10 years so I'd like to spend my hard gained money on something that I'm gonna be satisfied with.

**N.B. I LOVE crisp & clean sound (that's why I bought all 5.1 PolkAudio speakers) but I often listen to music and music is great at high volume (not meant to blow out the windows though) After all... am I best with harman kardon??