NHT 3.3s -- too big for my room?

Can't see why they won't work if you set them up as recommended. Your room is plenty big.

The only thing I might hesitate about is the 3.3's bass output. I've heard those speakers extensively in my friends system (much larger room) and they put out some of the lowest, most detailed bass I've heard. His system was the upper tier of Levinson gear. They're really impressive in that respect. They're nice speakers though...require some serious power to make'em sing. He had his right up against the back wall and they threw a very wide sound stage. Beautiful piano black finish too. Heavy as all get-out. I didn't know they were still made. I've seen them being sold used once in a while for around $1.5 - 2K. I'd speculate those bass traps are going to be very necessary in a room the size of yours.

Marco

Regarding power... I wonder if my Bryston 4BST will be enough for these?

I have mine in not the most optimal room (14' X 14') about 5 inches from the back wall and a little over three feet from the side walls. I power them with modified Forte 7 monoblocks, 75 watts Pure Class A and other times with my Threshold SA/3, 50 Watts pure Class A. I have used larger powered amps, but have settled on these(best sound yet) until I have a larger room and fined better sounding equipment($$$$$). Love it!!!!! They are heavy!!!! 125lbs each. Get someone to help move them around.

Forgot. The Bryston should be plenty of power and they don't manufacture them (NHT 3.3's) anymore. Check out their new Classic 4's if you have a dealer near you. They ship in a couple of weeks.