Can we agree, that the critical component for this is the power amp?
I don't agree with that. I think the power amp sims in the fractal are, for lack of a better word, perfect. If I wanted a cab in the room sound, I'd leave PA modeling on and run a hifi-style class-D amp with a high damping factor into a cab. I even know the cab and amp I would use.
Thanks to both things that Cliff has posted and my own research figuring out, among other things, how to run my passive "mastering" speakers well, I feel like I've got a pretty good handle on this.
I've also played a variety of vintage and boutique amps and heard a lot of concerts with every conceivable mix of guitar gear from small rooms to stadiums....when I'm in the crowd, I flat-out can't tell and literally do not care (the Bonamassa concerts are still cool just seeing all that gear being used, plus I'm a Bonanmassa fan...going to see him again in a few weeks).
I'm absolutely convinced that "amp feel" and "amp in the room" is 100% about acoustics and volume. And you only get that when you're on stage.
But, to the OP, I've done something close to that, though I didn't record it.
The second to last time I went to try out an FRFR (it was the Line6 2x12), they just happened to have a 1987 Silver Jubilee sitting next to it, so obviously I played it too. The guys in the shop were curious, so I replicated the setup (including a fractal model of the same cab, which sadly wasn't the SJ one with v30s) in my FM3 and we set up a switcher (it was a GigRig QMX that I had sold them a few weeks ago) and matched volumes as close as we could, loud but not stupid (it was around 100dB according to my phone). And we all played it. They weren't exactly the same, but the Silver Jubilee in the Fractal was a Lerxst at the time anyway....and IIRC there was an SM57 and a preamp "in the way" of the Line6 on the fractal side (I prefer IRs to the Line6 speaker modeling). So, still not at all perfect.
And we
all came to the conclusion that the Marshall was cool because of what it was but that either sound would work just fine if you wanted that sound. Once I started playing with my normal wet effects after the amp...literally everyone including a couple tube die-hards admitted that practicality would mean that the Fractal would win if you didn't have a team of roadies and techs.
They still didn't want to change, and I still think it's fun to play fancy/cool amps. But, the decision for me comes down to the fact that a Fractal fits into my life better. I love the sound, and I'm inspired to play. And I don't have to fight with the volume required for the vintage-y non-MV amps I prefer.
Oh yeah, the last mix project I did came with only guitar DIs, several of them. Honestly....I couldn't bother re-recording all the guitar sounds one at a time. So, I bought one of the Neural plugins to do it (the Tone King one). It was fine too....sounded great in the mix. I've played it a bit as well, and it sounds and feels good. It doesn't have the flexibility of my FM3, and I don't want to be forced to play through my computer....and the effects are mostly junk compared to the Fractal effects. But, that works too. I'm no longer opposed to plugins, but I'll only voluntarily use them when I'm mixing DI tracks.