Somebody convince me that I need an actual power amp, mmkay?

[Dolemite]

I guess I'm a dumbass (it's been said more than once ) but I kinda need someone to explain to me why an actual power amp intended for use with monitors is so much better than an average consumer-level receiver. I'm trying to determine the best upgrade path from a hifi monitoring system to a more "professional" setup, but still hoping to rely on my Pioneer VSX-D409 receiver (its OK to laugh) for amplification. I know this is probably the equivalent of recording heresy, but I'd still like to know why (and by how much) a power amp would be superior.

Don't be afraid to get technical, I can take it.

[Blue Bear Sound]

...The 2 biggest factors are the ability to handle high-transient peaks, and also to deliver extremely clean, distortion-free power, even if pushed a bit.

Consumer-oriented receivers generally fall short on both counts, the exception being the high-end multi $$$K ones.

Bruce