Just some additional food for thought on how much output is "room filling" since everyone's taste is different.
I use a single DVC15 in 6 ft^3 tuned to 17Hz in my theater room (24'x16'x9'). With our typical movie levels at -15dB below Reference, it's more than enough. Unfortunately, I can't remember what movies/scenes, but the times I've metered it, that's good for peaks in the mid 90dB range with all speakers/sub combined. Put another way, -15 can still be felt about 50' away from the sub and the theater room is a FROG that's fully insulated on the common wall with the main living area as well as having exterior doors between it and the main house...the previous owner finished the FROG after the house was built, so it was originally treated as unconditioned space.
Here are a few in room measurements that I have handy. The first graph is showing the DVC15 with Audyssey on/off ("on" produced the increased output below 25Hz). The second graph is a single of the 315HF I suggested above...3.5 ft^3 with 20Hz tune, but in my case it's not a BASH300 so there's no EQ from the rumble filter. Due to the lack of a rumble filter, I limited the start frequency of the sweep a bit. Both subs were measured in the same location at different times with different prepros...hence the difference in the >80hz response. Since the mains amp is powered off for sub measurements, the 315HF graph suggest there was a problem with the xover in my previous prepro. Anyway, these aren't max output runs, but they do illustrate what even modest 12" and 15" drivers are capable of. Measurement distance was 14' from sub to mic, mic is ear height and >5' from the nearest wall, subs are corner loaded in a 24'x16'x9' room, no EQ (except Audyssey as noted), no smoothing, no rumble filters.
-Brent