I have helped a friend years ago make a party bus. We went with prefab sealed box for 2-12s under each seat.
We put 4-12s on a Skar RP2K. He had a total of 48 subs on 12 amps. We put 2 6x9s on each side of each row. Each row on an RP150.4. 48 speakers on 12 amps again. He had his generator rebuilt to some insane number. Each row had 2 massive batteries that weighed like 150lb each. His wiring was close to 15k in cost. All were 2/0 and each row had 4 runs, 2 per battery/amp.
Im gonna look for the pics when I get home from work. All the amps were mounted in the center aisle and under plexi. Looked killer. Now, the subs he used were cheapie HiFonics. He had bought them in sets of 8 for like $300. The 6x9s were MB Quart Formulas. He got a killer deal on those crappies, er, Cheapies. $100 for 4 pairs.
After it was all said and done, it took us about 3 weeks to put it all in, and it sounded pretty good. Nothing to win any competitions, but it was just built to haul people and play loud music. It was done for about 2 years until we ripped it all out and redid the seating to be along the walls, facing inwards. Cut out almost half the seats, and the 6x9s were moved to the roof. Amps stayed down the center, but the boxes for the 12s were redone. Same subs and all, but changed to down-firing to avoid being kicked.
He sold the bus about a year ago. Had 4 stripper poles down the middle, light up acrylic. Looked permanently wet.
Had bubbles in the poles, lol. I'll look for pics in the am when I get home.