Home Theater Sub suggestions for 13x13 room

I have searched the boards here and it seems most articles are about the best "musical" subs. I am relatively happy with my b&w604s3's bass capability for music but I am interested in getting a subwoofer for movie watching and gaming. I don't intend to use it for music. Can anyone make any suggestions for subwoofers in the 700 us price range. I have considered the hsu research vtf-2 but would like to be able to go a little lower than 25hz. Any suggestions would be appreciated.