I can get a pretty nice discount for any of the Def Tech subs. So I'm wondering if anyone has any experience with them?

I have a Def Tech Pro Sub 80. I have no complaints about it, I think it does a wonderful job. I would like to go bigger/more powerful, but our duplex shares a wall with the neighbor. Granted theres been no complaints at all yet (Probably due in part to the concrete block wall/standard wall on each side of the blocks), but I don't really wanna open up Pandora's Box. ;)

the supercube subs are very nice you will not be disappointed

Well which ones are you looking at? That might help out. Personally, I think there lower end ones are not all that for the money (even at 60% off.) Like mentioned above, their supercube series is great especially the trinity =).