I have M-180s. Great amps, very clean and plenty of power. Tight bass, nothing "rolled off" about the treble.
There are a number of reviews on them. One compares them to another amp (forget which one) saying the M-180 sounds more "solid state" than the solid state amp.
If you're looking for a tubey sound then they are probably not for you, but if you're looking for clean and powerful amplification they fit the bill.