It is my understanding that all solid state receivers are designed to have a flat frequency from 20hz to 20khz. So sonically they should be neutral and not color the sound. If you adjust tone controls like bass/treble, or some of the built in DSP modes that affect the frequency or EQ, then you may introduce brightness or a laid back sound.

I think the only difference would be in the quality of the guts inside the receivers, but in the same price point they should be pretty comparable.

M80s VP180 4xM22ow 4xM3ic EP600 2xEP350
AnthemAVM60 Outlaw7700 EmoA500 Epson5040UB FluanceRT85