Hi humanflyz,
Thanks for this post:
A few weeks ago I had the chance to hook up with John DeVore (DeVore Fidelity) and we powerd his Gibbons Super 8 speaker with the Signature 30:
http://www.devorefidelity.com/gibbons.htmlThese are 90dB, 8-ohm, 2-way and it drove them with ease. I was very impressed with them and can highly recommendt them with the Signature 30. The Gibbons 8 is one sweet 2-day floorstander! John DeVore was also very impressed with that pairing.
At the last VTV show in NJ, I had the Sig 30 powering the German FJ "OM" speakers:
http://www.6moons.com/audioreviews/fj/om.htmlThese are 87dB, 6-ohm. We had Nine Inch Nails really cranked up loud (the track was "Sin" if my memory serves me correctly) and the Sig 30 pushed the FJs hard and clean.... again, no sweat.

There is a member here on AC who uses his Signature 30 with his Quads (I forgot the model...maybe 988?) and they are not the easiest speaker to drive, but he posted a few weeks ago with positive results.
A few months ago, I had the chance to hear the Sig 30 with Gallo Ref 3's (maybe 88 or 89dB)... another great pairing that I would easily recommend.
Long story short --
You are definitely NOT restricted to single-driver, high-efficiency speakers with the Signature 30. In your 10 x 11 x 8 room, either of the speakers you mentioned will be powered fine with the Sig 30. In the case of a 4-ohm speaker, you'll actually be able to get more like 40 clean watts of power out of the Sig 30. If you need more than that, the upcoming Sig 70 monoblocks will do 70 - 75 watts into 4-ohms.

I doubt you'll need it though. Remember, you have a 30-day trial period in case the Sig 30 doesn't have enough "ummmph" for you

Best regards,
Vinnie