I am myself running in a room 12.0078 x 16.404 feet(3.66x5 meters, coverted to feet
), with 2x Q900's and 2x Q700's
And I don't think it's too much even for such room.
If I am listening to music I am playing it in stereo over the two Q900's or all four speakers with the Q700's behind me, running trough a stereo receiver(oldie, a Pioneer SX-6000) with a lot of authority.
If you are looking for the best between the two and you're budget allows to buy the Q900's I am recommending the Q900's those are even better than the Q700's which are already very good in their own.
TV: Panasonic TX-P50VT30E
Audio | Receiver: Pioneer SC-LX72 (Pioneer Elite SC-25) | Speakers: 2x KEF Q900 for Fronts | 2x KEF Q700 for Rears
Audio/Video Sources | Panasonic DMP-BDT 310 | Pioneer PL-510 | HTPC using Intel i3-3220 16GB Kodi on Ubuntu 16.04