Two subs or not Two subs?

In a room that size, two subs might be better than one.
Adding bass traps would make a much better improvement if you do add two subs.
I use one sub, but my room is much smaller than yours.
Another idea, try one sub first, and if you feel like it's not ballanced, then get another. With the room being deep at the listoning position, one sub might work fine.
Good luck and keep us posted.

I agree with Zman.
If you buy 1 sub first, get some long el'cheepo (Rat Shack) sub cables and move it all around the room. You may be surprised at where it sounds the best.
Good luck

T series is for home theater; crosses over much higher than the S series. Get one S series and see how you like it; one may be all you need.