I own a SVS PC-Ultra sub. It does a great job in my existing space (18 x 14 x 8, open doorway). It could handle a larger area. Bottoming out is definitely not a problem. It's a very musical sub, in addition to adding slam to home theater.

I've also heard very good things about HSU subwoofers - particularly their top of the line model (under $1000 with turbo... a great deal). Since Outlaw's subs are designed by Hsu, I'd guess that this great subwoofing ability can be had for a lot less here at Outlaw.

If you have a lot of spare cash, there are some great options from Velodyne (DD series) and Thiel. These will set you back a pretty penny, but go a long way to off-setting room/boundary effects (one of the reasons I went with the SVS... it had a parametric EQ that could tame a peak I have in my room). They will also get you clean, sub-20Hz response.