25-31 PCi tuned...
My 20-39 PCi does a very good job in a 25x14x8 dedicated HT room. One option you may want to consider is picking up a 25-31PCi from SVS for ~$570.00 that would give you some serious bass (see here). Even bigger, a 20-39PCi for about $50.00 more, both including shipping. Also consider waiting for a B-Stock of one of these or a PB12.
If you wanted deeper extension from the 25-31, you could ask SVS to tune it down to 22Hz or even 20Hz, they should do it for no added cost. This would sacrifice a bit of output/SPL, but at 25Hz, you may be more than happy with its low-end extension without the tuning. If you did decide to have them do this, you'd essentially wind up with a 20-39 PCi for about $50.00 less and it would be a bit smaller than the 20-39. Not drastically smaller, but 8in. shorter, which might help in location placement.
I'd have a hard time believing you wouldn't be satisfied with the output and extension on a 25-31 PCi in native (25hz) or tuned (22hz) mode, these guys do deliver..