How many channels?

[keithwit1]

I have a 7.1 surround sound system. I would like to ad more power through a power amp or amps. i would like to add more power to the sub as well. do I need to buy a 5 channel amp and a 3 channel to make this work? or will a 7 channel amp be O.K.? please help. keith w.

[N. Abstentia]

You will need a 7 channel amp for the first 7 channels, pick up one of these bad boys:
http://outlawaudio.com/products/7125.html

I'm assuming you have a powered sub..the best way to upgrade that is to replace the whole thing. If you don't have a powered sub...you might want to get a powered sub. What kind of equipment do you have, anyway?

[keithwit1]

Yamaha Rx v-2500
Polk RTi8
Csi 5 center
FXi 5 Surrounds (4)
Energy 400 watt 10" Sub
Yamaha DVD c750

[kexodusc]

The cheaper (and IMO better) way of adding amps is to do so a pair of channels at a time. The 2500 is pretty darn powerful. Why not use it to handle the last 2, 3, or 4 channels of amplification.
I recommend Rotel or Adcom amps, only because they're cheap, sound great, are of excellent quality, and are very plentiful used on ebay or audiogon. But don't limit yourself to those 2 brands, tons of great amps out there.
I have an RX-V1400 with 3 power amps connected to it, the recevier runs the center channel, and that's more than enough for my 500 sq ft-ish room.