There is essentially no limit on sub insanity, even that is piddly compared to what is possible.
Someday when I build a house there's going to be an infinite baffle setup built directly below what will be my theater room.
Right now I'd be satisfied just to get out of my apartment so I can actually use my Tempest & 750W rackmount amp. It hasn't even been turned on in months, it doesn't take much at all to get the neighbors pounding on the walls.
Viper GTS