Basic Wiring diagram for Headunit to amp to sub.

[TbM]

oh kool ty. so looks like i really am gonna need to pull the HU out for it to work.

Oh and just curious as to why my amp has a socket that looks like it accepts a plug simular to that style. any idea what that is? :S

Probably Speaker level input but without a pic i cant say for sure, some amps can take there input from your speakers if your headunit doesnt have rca's, can be wired up to a plug like that.