My older Phase Tech PC 10.5s 3 way towers (mentioned above) are now in a room comprable to your dimensions. The dodds are never taxed and the vol on my Thor pre never gets past 10 - 10:30 AM ... usually it's around 9AM or less.
Your's are more efficient, and have an easier impedance load. 88db at 6 ohms should be tube friendly enough in that size room, so unless you go way low on power, like say under 20wpc, you ought to be fine. A BAT vk60 drove them pretty well in a 14x21x8.5 room... though bass was an issue there. They start rolling off at around 40hz, but in a smaller room eg., 10x11x8.2, the bass is fine. Sufficient in fact.
80% of the music is made in the first 20wpc.... so I hate to say just how much one needs on tap from any amp... I feel the considerations are too numerous, largely depending upon how loud you listen routinely, for example. How much head room is also a thought. Power reserves are a definite good thing, as much if not more so than is the power output itself. it's doubtful any of us will actually use ever ounce of abaiable power on tap achieving a prefered volume level, if even a moderate choice of amps is made. The main concern past power reserves, headroom, is certain freqs require more power to reproduce as the amp is taxed more... as the vol being turned up.
Power ratings of amps to the sensitivity and imp of the speaker alone isn't how I'd approach it. you, and the room play a big part too.
Given a speaker with 88db sensitivity, needs 1 watt to develop 88db SPL at 1M on axis, on paper it should only take 8 watts to develop 88db at a 4M distance which exceeds one of your dimensions. Consequently at closer range the SPL will have increased. Again... ON PAPER... and on axis or right in front of the speakers drivers (vertically and horizontally).
There are other considerations. I'd stay in the 50-60 wpc min power camp in that room with those speakers to be safe. Especially if rock is the main genre being tuned in regularly, and you listen at or above 93-94 db... which is pretty dog gone loud actually, if on avg. IMO.
true too is the note on matching the sonics of the amp to those of the speakers, as was already said. too much of a good thing, is too much.
Art audio makes some very good amps though I've not tried them meself. I understand they are suprising given their rated outputs. The Cary V12 is a good thought too. but it uses four more EL34 tubes than do the Dodd monos put together. the BAT vk60 uses eight 6sn7 input/driver tubes + 4 russian output tubes... more tubes means more $$$ when ya wanna roll in some different ones just to see what happens.
Good luck with your choice (s).
