what gauge should i use

use the 2 ga from batt to d-block, and short runs of 4 to each amp.  I'd put a 150A near the battery, 100A to the 1000w, 50a to the 500w.

2 gauge to distribution block smaller wire to amps plus same size for grounding, so how do u install the wire to capacitor plus do i use one grounding point for capacitor and both amps?and why all the fuse in the back?

Suggested capacitor wiring diagram

If you already have the cap I guess you should go ahead and use it.  If your amps have fuses in them, the fuses in the back are really not neccesary.  Just remember 150 amp fuse at the battery and you will be OK as long as you use nothing smaller than 4 Ga. wire

Nice picture! Paint works wonders.