I play in a band with a friend of mine who has a m6 Carbine. I really enjoy using his amp. I also went down to guitar center yesterday to try out some Mesa cabs (my ampeg cabs are not doing good at all.....) and they had a M6 Carbine there. At about 20% volume it was rumbling guitar center. I was playing a MM Sterling, M6 Carbine, and a Mesa Powerhouse 4x10. It sounded amazing.
I agree that the big block is more of a..."rock/in you face/loud and grumbly". And I don't fully understand the freqeuncy and the dual mid knobs. I don't know. The M6 just seems more appealing to me. And it's physically lighter.
