I'm not a big believer in "bright" receivers. I do think some sound "thin" (typically ones with wimpy amplifiers) and arguably those might sound a bit better with speakers having a depressed midrange, but I don't think you are going to find a noticeably different sound from one receiver to another.

Not everyone agrees with this, however...

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8