for a bargain setup mate......
you can currently get some JBL packages at Motor World, your talkin £169 at most which is the 4 channel amp package with 12" sub and box, all you would need is a wirin kit which would be about £25
also, some JBL components are on offer aswell, usually £99 but they are down to about £55 now......GTO506c IIRC
all that would leave you cash to spare