I would use the 5 channel for the cabin speakers and subwoofer and get a seperate amp for the tower speakers.
Couple amps that would power the pro60s well. Anything that will deliver 150 watts to each tower speaker would be a good choice.
http://store.earmarkcaraudio.com/Xca...0&cat=0&page=1
http://store.earmarkcaraudio.com/Xca...cat=330&page=1
http://store.earmarkcaraudio.com/Xca...4&cat=0&page=3