I had an M6, its a beast, way underrated as far as volume output (perceived versus specs) IMHO, way louder than the 600 watts it claims, one negative, and only a negative if you are looking for versatility, is that there is definitely a baked in sound to this amp, not bad, not good, there just is. Then again, same with MarkBass, I had a ton of their gear also. If I were choosing today and these were my only 2 choices, it would still be the M6.
Rock on.
Rock on.