Need more volume, cheap. Any advice?

Just had installed three pairs of Klipsch 5800-CDT-C ceiling speakers in three different rooms and got a two-zone Denon receiver (AVR 1910, 90 wpc). The kitchen and living room are on one zone, using 5 channel stereo, and the tv room is zone 2. These are the only speakers in my setup. The problem is I was hoping for deafening volume when needed (rock and dance) in the LR/Kitchen and can only get close to that when I turn the receiver to 100%. So, I was thinking of changing the LR/Kitchen to zone 2 because I can send the zone 2 output to a second amplifier. I don't need perfect sound, but don't want distortion and don't want to blow the speakers. Can anyone recommend a four channel amp that would provide more/better power than the Denon receiver? Something I could easily get used for $300-500 would be perfect, if such a thing exists. Though not ideal, I could also probably get rid of the Denon and start over, but would still need inputs for TV, ipod, DVD, etc. Much appreciated.