The advice for you to consider the EAD powermaster was pretty good. I have a pair of M-3si's that I bi-amp with a Powermaster 1000 (5x200 watts). It sounds great. I also have the bass below 65Hz crossed-over to a pair of Mirage BPSS-210 subwoofers (through a modded FX-3) and that helped the sound of the M-3si's significantly. Soundstage is wide and deep (be sure to have your M-3si's a good distance away from the back wall). The Powermaster has clean, is just on the warm side of neutral, with a laidback sound with plenty of muscle. These amps are a bargain on the used market.
As suggested by Sogood, you might look further into the pre-amp upgrade. I've found that makes a big difference, and the clarity.neutrality of the Powermaster will let you hear the differences.
As suggested by Sogood, you might look further into the pre-amp upgrade. I've found that makes a big difference, and the clarity.neutrality of the Powermaster will let you hear the differences.