Without knowing your budget I'll throw a couple out there.
As an Electra 926 owner, I can tell you that my 45W CJ tube amp in my 14x15 room is just fine. From what I saw in Hifi-choice, the impedance dips to 3.5 ohms at 50 Hz or so but the phase isn't bad and the senstivity is indeed higher than average for both 926 and 927s.
However, I would say that 30W is a minimum and even then, you will need to keep the volume somewhat under control.
You only want monoblocks? That will limit your choices significantly but if so, the Cary six packs may be plenty of power and sound great. Arthur