Always smiling...!
The combination of the KPA with my 2 QSC K8 speakers works fine. Pressing CABINET shows a dozen of cabs. But do I need them when I now have external speakers?
See, there's still some misconception on your side.:)
A profile contains a whole signal chain: amp, cab, plus how the cab is microphoned.
You want to amplify this signal chain as neutral as possible.
The QSR's as such are a good choice because they are FRFR (full range flat response).
But IF you want to hear a Marshall Head with another cab, e.g. a Mesa you'll apply another cab to the rig.
You can apply any cab of any rig to any other rig.
This gives you lots of options.
See also the WiKPA in my sig...