I'm looking for a small amplifier that I can hide away in my car. Hopefully something for 40-odd quid from eBay.co.uk - that kindof thing.

It needs to be a 4 channel unit for driving basic factory-installed speakers - I might upgrade the speakers in the coming months but I really not looking for a boom-box kindof affair!

In terms of size, well, I think I've got about 300 x 150 x 50mm available - any suggestions on what I should be searching for?