I use FRFR for the Axe FX Ultra. I was considering doing a little amp/cab stuff as well, since I miss something about the way the speakers are pumped by certain amps. The trouble is, I don't understand all the issues well enough to zero in on something practical. Probably certain sounds work one way, and certain don't. I notice that one person is running the two Axe FX channels, one into mixer/pa, and the other into a guitar amp. That's something I've wanted to do. If only there was a way to have a stereo set up that had routings that felt like a guitar amp, and routings that felt more like the FRFR thing. I guess people run from the FX send, right?
Ideal processor placement: before and after amp, <i>not</i> in amp's fx loop
Then there's the "running with amp sim but not cab sim" through the entire signal flow of the amp, right out the speaker level outs, but fine people have constructed a conversion to change that signal into a headphone level signal. They call this a "headphone adapter/attenuator" for the power amplifier.
Headphone Adaptor for Power Amplifiers
In my sadly uneducated mind I tend to think its more ideal to grab the signal AFTER the power amp is done with it, and it would be great to have a stereo version of that, and by the option of the aforementioned conversion from cab signal into headphone signal, choose to send one or both channels to either or both of the Axe FX and/or a guitar cab. Now that's what I would like, a guitar amp whose primary purpose was not so much tone manipulation, but providing the signal flow to get the best of both worlds, natural driven speakers, and Axe FX cab sims..... Simultaneously, In Stereo, and switchable, without having to pay for two guitar amp rigs.
That way I have a setup that works in my room with my pc, and at rehearsals, and clubs. Oh, but I forgot, its only a dream.