Tyson - my room is right at 2500 cubic feet. I started with one EP600 and had to play with placement quite a bit to find a position that sounded good (ok, great) in my main listening position. What really helped me was adding a parametric equalizer (Behringer Feedback Destroyer - ~$150).
If your room allows for several different placement options for a single sub, you should be able to find one location that sounds good in your primary listening position. If you're stuck with only one or two spots where you could position a sub, then two subs would give you smoother response and rely less on perfect placement.
If you're concerned with smooth bass response throughout the room, you'll probably prefer two subs. If you just want it to sound awesome exactly where you sit, you're more likely to be happy with a single sub.
The compromise position is to get one sub now, the biggest/deepest sub you can afford, and to enjoy that one until you can afford a second that matches the first. Like Jay said, you may find you're just fine with a single sub and never look back.
Jason
