Those Tubeworks MOSVALVE power amps are very cool indeed. They've been popular with pedal steel players for a long time. Many pedal Steel players have found themselves in a similar boat as we are going after the Jerry thing. High headroom, tube preamp for a sweet-clean factor, and power that has a warmth to it, not just a clinical sterility. Paul Franklin has been the #1 top A-list session player for decades now, and his primary rig for a long time was a Boogie studio preamp into a Mosvalve power amp into a pair of 12" Peavey Black Widow speakers.
The MOSVALVE is cool because its output is driven by MOSFETs. A MOSFET is a transistor with some tube-like characteristics. They have a warmth and a sweetness when run clean, and they clip in a somewhat friendly manner. And those MOSVALVE amps in particular are guitar friendly. Not exactly a Mac sound, but totally viable for our purposes. I'd say the Mac has a slightly darker or warmer overall characteristic and when the Mac clips, it's a bit subtler in it's harmonic content. The MOSFET amps are a bit more lively and maybe crispy with their distortion harmonics, but the harmonic quality of the clipping dirt is pleasant, not nasty like with some normal transistor amps.
Hafler is another consideration for a MOSFET power amp. There are tons of old DH-200's and DH-220's out there. These are really nice stereo and studio amps and work great for clean pedal steel or Garcia guitar approaches. The more modern Hafler trans-nova series amps are also out there to be had. Again, those are very good sounding stereo/studio amps as well as being very nice for these clean guitar applications. The older DH-200 and DH-220 may be more raw and pure like a Mac in that they don't have all that protection circuitry like the Trans-Nova amps do. So that may be a good thing.
But back on topic, yes power amps definitely have an effect on the sound. Some people will go for extremely clean and loud and boring sounding power amps that don't really impart any character and then rely on the preamp signal processing to develop all the mojo. Others will approach it like Jerry did and consider the entire system as part of the tone generation, with the power amp being a critical factor. But all that said, I think that when doing this clean approach, the preamp is the more critical factor as that's where the real tone shaping, EQ-voicing, and fundamental gain staging takes place. There's more guitar tone development taking place in the preamp stages for sure. That's where the tiny things like resistors, tubes, and capacitors all become significant contributors.
... and it's just like any other day that's ever been...