no budget
hmmm
get 2 tc sound lms-5400 15's(unlimited power handling) and 4 soundstream xxx6500 amps and strap them(2 amps per sub 13k per sub ..depending on electrical)
and if u want more power get 2 soundstream xxx10k amps and strap them(2 per sub will give each sub about 20k depending on electrical)
and build a 6cube ported box tuned to 35hz...or a 6th order bandpass..either box will get u seriously loud
80