Be sure to turn off any equalizers with the auto-setup feature. Sometimes, the auto setup features of receivers can mess up on a few things, especially frequency. Look in your manual to turn that off, and see if it is an improvement.
I know Pioneer has one of the best auto setup features on recievers in the industry, but many still think the best tried and true way to calibrate speakers is with an SPL meter and a Test DVD. However, I'm pretty sure the reciever should have gotten the individual speaker volumes set up correctly, so you shouldn't need to worry about that.
I hope that helps
.
