I picked up the Dayton SUB-800 to use in my bedroom last week. I've got to say that it impressed me. On sale for $69 right now, so it's an even better deal.
I am using it in a bedroom (12x16) to add some warmth to a pair of Selah Aura Jrs. (Dayton ND-130 woofer and SB Acoustics SB-29 tweeter) and it sounds really good. (I have 2 SVS PC-ultras in my main listening/theater system)
I wouldn't build a big home theater aound the SUB-800, but to shore up the bottom end of some small bookshelfs, I think it is a real bargan.
No, you aren't going to get 20 hz, but in most rooms I think it will get close to 30hz, and if you are using two of them, then I think it's even better. It's definitely not a one note boomer, so if you keep the volume reasonable and don't expect them to go super deep, I would recommend it.
If you can't afford to step up to the big boys from SVS, Hsu, etc. ... I would recommend the Daytons.
Heck, if you have the room, the Sub-1000 is on sale for $89 now. Get two of them and don't look back.