I can only relate my own experienc with MMGs and tubes. I'm
using a pair of Quicksilver kt-88s to drive the MMGs. I do use a sub with a high pass filter which eliminates the lower frequencies from the MMGs. I listen to jazz,classic rock, new age, etc. My room is about 13x15 and then opens up to the kitchen. This effectivey increases my room dimensions to 13x24. I listen at about 80-90db and that sounds loud enough for me. I would say a sub is essential, and the sound quality is, to me, terrific. I'm using an Opera Consonance pre-amp and AES phono pre-amp, all purchased through audiogon, except the MMGs. My previous speakers were Acoustats driven by a Parasound hca2200 and the Quicksilvers. I retired my Acoustats and Parasound to the bedroom (I have a big bedroom) and couldn't be happier with both combos. The MMGs are a much easier load than the Acoustats, which dropped below 2 ohms at higher frequencies, not to mention their fairly severe phase angle.
Don't mean to ramble on, but to answer your question, with you musical tastes and room size I believe it will work fine. The kt88s are rated at 60 watts per channel.
Jim