i have 2 pyle pld15wd (15" 4000 watt) subwoofers and a pla-2260 (2ch 4000 watt) amp and was wondering on what kind of box to get or make, and how big it needs to be? on pyle's website it says each sub needs 8.689 cubic ft, but everyone i've talked to about this says that they don't need anywhere...