I just replaced the amp in my truck. After looking at all the different 5 channel amps out there, I went with the Viper Audio 1100.5. It's not a brand name like Alpine or Kenwood but their parent company is Directed Electronics Inc. which is one of the largest mobile electronics companies in the world. The specs on the amp were very impressive and now that it's installed, I love it! I highly recommend this amp!

http://www.directed.com/audio/viper/amps/amp_multi.asp