If you want to go DIY, take a look at the Eminence LAB12 drivers. They are used in several very high end subwoofer designs, and are a tremendous sounding speaker. They are low inductance, and multiples of those with a good pro amp will pressurize your room.

You could easily build a system with 4 of these drivers and be under budget - and this will give you SPL to spare along with incredibly good sounding mid bass.