I traded the M-Pulse for the M9. The M-Pulse lacked of clarity, clean and punch. It was more vintage oriented. Very well designed except for the parametric EQ I use SWR Goliath III cabs. The very first time I plugged my bass into the M9, I thought I was playing my SVT 4 Pro. The way I EQ my SVT4 is exactly the way the M9 sounds everything at noon. Super dynamic, chrystal clear and clean, super modern. That's actually what I want to here from an amp. Plus a very particular grain. Probably the Mesa grain, but pretty interesting and somehow unique. Usually described as "glassy". It's actually pretty true. The first thing that actually freaked me out was the master. You simply can't go past 9 or maybe 10 o'clock. Nor it will just simply rip your face off!! It's actually wayyy to much. Unlike the MP600, I really like the graphic EQ. You immediately know how to use it. The compressor is the same as the MP600, very efficient, and gives you way more control than most of amps on the market. The amp comes wuth a 2 buttons foot switch. I kind of regret the M-Pulse on this actually, where you had the 4/5 (depends on the version) buttons footswitch providing you more control over the amp. But the amp is not perfect, it has some weird things on it actually. First thing is the taper of the master. Way too sensitive! The mute button also. You have to pull the master. But the master is so sensitive that you might turn the master without even noticing when pulling it, ending with a weak sound or deafening sound. But the worst for me is the effect loop!! Come on Mesa..... Who places their effect loop after the master!!! This made my TC G-Major totally unusable with the M9 as it ends up making so much noise with it. And it's dead quiet with my SVT 4. If I had to choose between my SVT 4 and the M9, I might go for the SVT 4. Better design to me, more bells and whiles, pretty much the same sound. But I'm actually having a looot of fun with the M9. I'll try to gig with it to see how it sounds on stage. And then I'll make my choice between the two. But I don't think I'll get rid of the SVT 4. It's a great gigging amp. The perfect Mesa amp would be a mix between the Mesa M9 and the M-Pulse 600. THAT would make an awesome head!!