Also, carver is a name I came across with some rather powerful amps for relatively low price. The amps tend to be on the lighter side though (<20lbs). Would anyone recommend this brand to drive the M1's?
Go with the Heathkit AA-1600 or AA-1800. I've used a fairly beefy high current Carver P175 and currently use a Heathkit AA-1600. The Heathkit is crazy good for the money and has an engaging combination of crunt, current, and very musical, non-clinical neutrality. Good resolution for the money too.