DON'T USE MAINS POWER FOR JUST ANY COMPUTER FAN!!!
You can only use mains power if the fan is from a
power supply, usually right at the top of an AT/X case. Pluging a regular case or CPU fan into the wall will kill it (they run on DC or AC)... possibly with some good fireworks too.
I wouldn't see why that wouldn't work if you have one, I say go for it. If you find it doesn't give enough cooling, try DigiKey here:
http://www.digikey.com/scripts/DkSearch/dksus.dll?Criteria?Ref=136218&Site=US&Cat=32440856If DigiKey doesn't have one you like, you could try Newegg.com or any electronics or computer store. I'd still be tempted to go with something from DigiKey, but it all depends on how much air you need to move. Usually a 120mm fan running around 1500rpm will move approximately 53 cf/m (cubic feet of air per minute). Should be enough, but DigiKey has things listed into 117cf/m, which should be more than plenty. Not sure what the original fans were rated to.
To wire the fan in, you could go with what
rodl2005 said and give it its own plug. Or, if you're adept with wiring and don't mind the heavy duty soldering AND HAVE WORKED WITH MAINS WIRING BEFORE (this is important, mains isn't something to tool with randomly), you could probably wire the fan in where the amp's power cord connects. Alternatively, if you're really handy and don't want the amp running all the time, you could wire in a switch for it in the back or something. Where you attach the wires really depends on what kind of amp it is, I suppose.
