I am installing this amp, and it came with a 4 gauge power wire, and I have an 8 already installed, is it necessary to switch them, or can that amp run fine on an 8 gauge?

I'll go ahead and work on the speakers for now, but if anyone can answer, the sooner the better,

 

you could get away with the 8 gauge, but since the amp came with the 4 awg, might as well put it in. should be 4 awg for anything near 500watts anyways. also leaves room for an additional amp later..

 

I agree. Might as well run the 4AWG so you can upgrade later.