Hey guys this has probably been covered but I couldn't find it. I have Ef fairmont with stacker can I wire a new amp up easily enough or am I better off just getting a new head unit.
I take it there are no RCA out on the factory head unit???

Really depends on how keen you are. You can wire a amplifier that has high level inputs and a built in low pass filter (if you are only using it for sub) up to the factory head unit without too much trouble. The easiest way would be to tap into speaker wires going to the rear speakers.