Have been running my fronts (RTi10s) via the assignable amp feature on the Yamaha 5990, so it was using the surround back and the main amp to power the fronts. It sounded better instantly, a great deal better in fact, probably due to the fact that the RTi10s are a bit power hungry for that receiver.
But I blew a tweeter recently, and I figured I was driving that receiver hard and probably getting some clipping.
So today I took posession of an Adcom GFA 545II (100wx2) amp.
Connected the preamp outs for the front to the amp, and the amp to the speakers. Reran the YPAO auto-config, and gave it a test.
YIPPEE! Clean, powerful, and sweet! Sounds better than the bi-amped setup previously, without a doubt, and that sounded nice. Much more "presence" to the speakers, very impressive!
And now I have the surround back amp back for them.
I fear this was a bad step for me, financially...