+2 to what JohnK and Tom said. However, if the system was properly level matched you may have still noticed some slight differences ie. cleaner, crisper sounding at louder levels vs. the receiver's amp section. I have noticed this change and felt the mid bass punch was better with separate amps vs my Denon 3808's amps. You have to figure out your own cost of diminishing returns point is to justify going with separates, IMO, for me right now my 3808 is just fine.

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70