I would strongly encourage someone to buy the equipment and try it in their own home. That's the only way to really hear differences; real or imagined.

Personally, I've purchased multiple AVR's at the same time for back-to-back testing and I've definitely heard differences in the sound, brand A vs. brand B. I won't argue that it's the amplification sections making the difference, but I think it's naive to believe that every brand's implementation of sound processing is identical. Chips are different. The code driving those chips is different. The design architecture is different. Then there's each manufacturer's implementation of room EQ too; Audyssey vs MCACC vs YPAO.

So ultimately, yes, I think different AVR's can and do sound different from one another.

M80v2 | VP150v2 | QS8v2
SVS Pci+ 20-39
Emotiva UMC-1 & LPA-1
M22ti + T-Amp, in the Office