All of your wiring should be 0 gauge. That includes big3 and amp kit and everything you use. OFC is preferable. I think that if you got like 2 hds312s on a sq 2200, that might be really nice. Or you could not go soundqubed and go with something else like Skar VVX if you aren't wanting to run that much power. If you go above the 1500 watt spectrum, you are going to need a 2nd battery. If you go above 2k, everyone is right when you say you will probably need a HO alternator. I would think 2 hds312s and a sq 2200 would be a nice pair, if you want to keep everything the same and on sundown. Or, you could go big and buy a hdc318 and a sq 2200.