Receiver for pre/pro?

Jer, it is pretty hard to have a warm-sounding receiver without a warm-sounding power amp section. Pre-amps tend to be more neutral than power amps. So, if you bypass the power amp section, it is a crap shoot as to what the tonal quality of the pre-amp section is. My bet is it would be more neutral than the receiver as a whole. Adding a bright-sounding power amp will probably result in an overall bright sound.

My recommendation is to get as neutral-sounding of a power amp as possible. You will probably own it longer than the receiver and a neutral amp will always be the easiest to integrate into another system.

Forget the receiver as a pre/pro! It's still not as dynamic (nor usually as resolved) as a dedicated pre/pro! Receivers are usually softer in the dynamics department.
But, yes, amps in receivers really blow! You'd do better outboard amp-wise..and better, yet again, using outboard pre and amp.

I just added a Sherbourn 5/1500A to my Sony DA4ES receiver. The sound is clearly tighter and more controlled, but not as big a difference in the bass as I had expected. And as Flrnlamb has said, the dynamics are not that much improved. I have yet to really crank it up on a movie yet, so I may see a bigger difference then.

I do need to investigate just how good the interconnects are that I just got to hook the amp to the reciever. They are Belden 1505F from Blue Jeans Cable.