He needs 0 gauge for that amp trust me!!!! My mate has the same amp at 1500rms, and was running 4 gauge at first and it doesnt sound very good and was getting serious voltage drop issues. Once he got the 0 gauge in the voltage drop issues stopped!
Youl will probably have to drill a hole Will, I have done so to get my 4 gauge and 8 gauge wire through the same hole! Getting the side panels off can be a bit tricky the first time you do it as your scared of breaking things but just give it a good tug, would be a good idea to get spare clips from seat though as I lost a few and broke a few and now the rattles are doing my nut in big time.
Think there are a couple amp install guides on scn iirc, have you got crimpers?