I am planning to build a dedicated HT with a 7.2.4 setup. My room size is 21 ft x 15 ft x 9 ft. I will use the room for movies, music and games (33% each) I am confused between the following subs - A pair of the SVS SB 4000's or a pair of the Rythmik F18. I am getting both for a similar price. The issue is I will not be able to demo either. Kindly help! Thanks.