I have to agree with Bradical. I use my Denon 2313ci with a pair of Kliptsh RB-81 mains bi-amped, and can hear a significant difference. I get a more profound bass and cleaner, slightly brighter highs -- no change in volume, just a better overall sound. This is most noticed when playing stereo tracks only, I don't really hear as much difference with 5.1 audio, unless it's something like opera with the orchestra on the L/R channels and the singers in the center, in which case the orchestra has a better "presence."
I would definately recommend giving bi-amping a try and see if you like it better.