Kent--
I went through a similar evolution with my amp rigs... I used a Johnson JM150 religiously for a while before switching to a Triaxis/2:90 setup. While I loved the Mesa tone, the rack rig was a little more complex than I was shooting for, plus I pretty much had to haul around the rack, a cab, and a MIDI pedalboard just to jam. So I decided to simplify...
After much looking around, I ended up with a Mark IV combo. I absolutely love it! Very flexible (took a while to find my ideal tones), and comparatively simpler than the rack rig... I can have the full blown rig with
extension cab, rack FX, & pedalboard, or I can be lazy and only take the amp (sounds great either way). With the 3 channels and the switchable EQ, it acts more like a 6-channel amp. One great thing about the Mark--you can change the modes (Class A, triode, half power) so that you get awesome distortion at low volumes (great for recording), but then you can switch the modes back (Simulclass, Pentode, full power) for the full 90 watts. And for the record, I don't think I've ever had to turn mine up past 2.5 in a live setting.
For MIDI control, I bought a Rolls/RFX RP-93 Patchwork, which can switch the 3 channels and the EQ on the Mark. I use a Ground Control on the floor, although pretty much anything should work with the Rolls.
No matter what you decide to do, good luck! If you have any questions about the Mark IV, let me know!
--Brent
PS--For the record, when I bought my Mark IV I also got a Nomad 45 for a backup amp. The Nomads are killer amps, too, but I like the Mark IV so much that I'm planning on trading the Nomad in for a second Mark IV!