Just out of curiosity, did you check to see if there was an impedance mismatch between your amp and preamp? I had a similar problem with an Audible Illusions preamp going into an Ayre V3. I could not get past 9 o'clock on the preamp without blowing myself out of the room. It was because the V3 had a 10K input impedance which was not high enough to work with most tube preamps and not because the V3 had too much power.
If you have already looked into this ignore me but my experience with Maggie's (2.7's only many years ago) is that they like lots of power to play well. Good Luck!