Amp cooling

[Jack]

Planning on installing some new audio to my boot, in which the amp will sit behind a perspex window. I'm going to put a couple of small fans in as well to help keep it cool, but I only want them to come on when the amp is on - so whats the best way to power them?

[General Baxter]

off the remote wire then to the earth, done something like it before but can not really remember :|