The PSW108 seems to be very close to the PSW10 which is a very lack-luster sub. If you're going for HT go for the largest sub you can fit/afford. Keep in mind these are budget/entry level subs so performance will reflect it this. If you're expecting response in the 20's you'll be let down.
Polk PSW111 $150 - Smaller in size with a 8" driver but much more power this should out preform the above unit. This is also the lowest I've seen the price.
Pioneer SW-8MK2 $160 ($100 for prime members) - Another smaller sub with mixed reviews but the price might make it worth a look. Getting two might be good if you want to remove some nulls in your room. If you're not happy you can always return it. The down firing driver my be a benefit if you have small kids that like to poke things.
Dayton Sub 1000 $135 or $120 at Parts express - 10" driver in a larger cabinet. This is a budget sub that will get the job done for HT use in a small room.
Dayton Sub 1200 $150 - The larger brother of the above unit. The 12" version is pretty big so make sure you have room for it. Not the lowest digging sub for it's size but for the price this will work for HT use.
Klipsch K100-SW $150 - 10" with a decent amp this should do the job.
BIC RTR-12S $150 - Another 12" sub at a budget price. BIC normally had solid offerings so I would expect this to do fairly well.
Did you get it? I have two of these and they really do rock. I had one at first and it did a decent job for the room, but I really wanted a second one for esthetics and the volume increased since w have the two subs now. Wall light fixture shaking. I plan to get an isolator for both to minimize the shaking of the walls and light fixtures.