I had a purple stripe MKIII that I really loved the crunch channel on, especially running it in a stereo rig. i could get that "on the verge of break-up" sound that was really fat and singing, unfortunately it would be out of balance volume wise with the clean and lead channels. I was living overseas back in the day and came home to visit family in southern california. I brought the head chassis only with me to send to MB and have the vol 2 mod done along with a maintenance check and some other stuff. When i returned back overseas and installed the chassis back in the combo case and fired it up, it sounded great, but the crunch channel had lost the "mojo" it had before. I could balance the 3 channels now, but crunch was actually thinner sounding and it would not get that "on the verge of break-up" crunch. I had to toy around with the lead drive too much now to get any sort of crunch on the "crunch" channel and i would have more distortion then I needed in the lead channel.
Sad to say I had to sell that amp, I needed the cash at the time. But i've always thought that I would have had the vol2 mod reversed or contacted MB about getting the "mojo" back in the crunch channel in spite of the vol mod.
i've since "replenished" my mesa stock with a LSS, MKV:35 and a TC50. Love them all, but sure do miss that MKIII. I might have to scope out a used one, but just for home use cause they are "heavy" to haul around, lol... thanks for bringing back some memories...
peace