Well, I bought a Nomad 55 2X12 combo with everything but graphic for a really good price a little over a month ago, used in mint condition. Before that I had used a 1987 Mark III fully optioned with wood cab. I could seldom get a sound I liked out of the Mark. I quickly found several on the Nomad. Several of my musician friends were with me and they said "the loudest 55 watts we've ever heard". When I really began using the Nomad, to the good I found that I could get settings where distortion could be controlled by hardness of pick attack more so than any amp I've every played through. To the bad, I couldn't dial out all of that "Mesa nasal" sound. To remedy that, I put a good ten-band active graphic EQ in the FX loop. Found the "nasal" at about 500 HZ, and cut it out. I can't go back to the Mark II after the Nomad experience, and am selling it. Lead gain and power? I have my Ch. 3 gain set at one o'clock and get almost infinite sustain -- which is available with a higher gain setting at the expense of clarity. Like other posters here, I use very few effects. Only the EQ and a digital delay are in my FX loop -- and the delay is set only to compensate for small practice environments and isn't used at all in larger venues. This is the only amp on which I have used virtually no effects in a band environment and still like the sound.
If anybody can't "cut through the band" for solo work with a Nomad, they need some sound reinforcement help! For them, few Mesa's are going to "cut it" by themselves. I could "crank" the Nomad in Ch. 3 and blow out windows, if I wanted to.
It is interesting to note that Carvin copied much of the Nomad architecture for their V3, three channel amp, but added more EQ in the overall master controls -- much as I did by adding the ten band graphic.
Needless to say now, I do love this amp!
Now, I hope others will post on the 6L6 vs. EL 84 question.