what size? What room do you have to work with as far as a box? How many subs are you wanting to run? 1,2, 4, 6?...Are you running the amp for spl or sq? 4 oms?, 2ohms? 1ohm? Do you have the electrical upgrades done to support that amp at 1ohm due to the 20 - 30% loss in efficiency vs. 4ohms?