I too am trying to decide on which to buy; in my case either a PB10-NSD 10" box, or their older 25-31 PCi 12" cylinder (both currently discounted, and about $100 more for the PCi). I will use mostly for HT and R-n-R music. Equipment has changed to include an Onkyo 806.
I don't have a 2000 ft2 room, but rather house. The room is actually about 8highx15widex15deep including the stairs, but since it is on the 2nd floor, the right side is open to the 1st floor area (only rails) while three doors open into the room and stairs go down across the front (as viewed by the seats). The stairs cross the field of view from the couches, with the TV mounted on the wall on the far side of the stairs (very difficult to wire and hang but it was the only open wall, and it has really opened up the room). I will have to place the sub in a shallow corner next to the couch, behind the couch (on the 'wall-less' side, or in a corner of a small walkway set back from the front of the room (to the right and farther back of the TV). I have the electronics on a shelf above that area.
The amps and output appear similar to me, please correct me if I'm wrong. I won't live in this space forever and wouldn't be opposed to upgrading later (or building my own), but will I get appreciably better sound from the 12" cylinder although they have similar powered amps, especially at $100 more?
Thanks for any info/opinions.