Dual subs will give you a more even and consistent bass sound throughout the room. A single powerful sub will give you more bass, but it will be more erratic in both the frequency response and in different areas of the room. If you really only have one place you sit where you listen to music, it might be worth your while to get one powerful sub and find a good location for it with respect to your primary listening position. One thing I woudl encourage you to do for a more visceral feel is to use near-field placement if you can, this is where you place the sub very close to the listening position, like right next to the seat or right behind it. Also, if you decide to go for a variable tuned sub, like the Hsu subs, the Rythmik, or the higher end SVS subs, use the all ports open configuration, that will get you the most punch.