Room size too big for Sub??

My new, bigger, audio/HT room is 303 SF and 2800 CF. The REL Strata III sub just isn't cutting it for me for home theater. It gets pretty low but lacks punch, and placement away from the corner doesn't help.
Do I get a larger sub, (Revel B15?), a second Strata, or upgrade to 1 REL Storm for larger capacity. I'm not looking for loud, just strong, deep, accurate, dynamic and solid bass reproduction. All suggestions appreciated.
I'm using a pair of Strata III's in a 450SF room w/ 10'
ceiling. It works fine, but I'm not sure it's any better
than the single sub. Positioning of the sub is CRITICAL.
Before giving up on it, try moving it to different room
positions. Sometimes the most effective position would
appear at first glance to be the least likely.
My gut reaction is that your problem is not so much the capacity of the sub to produce sufficient volume in your room, but the accoustics of your room itself. You may have a substantial suck out in the low bass due to room placement, location of the listening position, or the room's dimensions.

Buy a Radio Shack sound level meter and a test disc with bass tones and shck out your set up and experiment with placements and see what happens before you venture out buy bigger subs. Your room really is not that large.
One thing I have found that helps with this situation is to place the sub in the listening position...Then walk around the room and listen to where the sub sounds best. More often than not, this is where your sub should be placed in the room. Try it and see if it works for you!