You might want to actually check stock with Hsu on Monday as they are having a model change to the new improved 250w Piano Black VTF-2 MK2, so the current special is a closeout deal. I know from the Hsu forum that stock was pretty limited at that price.
That is a decent sized room. Impact and SQ are very subjective so what may be my preference may not be yours. Both my VTF-2 and my VTF-3 are in smaller rooms but I am no where near both of the subs limits. Positioning the subwoofer right next to the listening couch would be the ideal position to "keep impact" in such a decent sized room. However FWIW in Tom Nousaine's large room (7500 cu ft) 13 x 23 x 18 ft with large openings (not a small room either) the corner loaded VTF-2 using a 10% distortion limit, averaged a maximum output (at 1/3 spacing between 25-63Hz) of 109.70dB while it measured 20Hz at 93dB and 25Hz at 99dB under the same conditions that Tom uses in his room.
If you really want more headroom in that big room without spending a lot more $$$ or because of WAF you can not put a subwoofer close to the couch - although seriously - in that room I would still look at this position first ....... I would take a good look at the (shipping on Monday) Hsu STF-3 which is a VTF-3 MK2 without the glossy paint and variable tuning. In direct comparison to the VTF-3 MK2 it has the same enclosure, same driver, same orientation, same Bash amplifier (I am not sure I believe the less 50w story from Hsu - 300w vs 350w) Due to the Piano Black finish the VTF-3 MK2 will now not ship till at least the 12th Feb.