I may be way off base, but wouldn't using a guitar cab defeat the purpose of the profiled amps in the Kemper? How is the profile you're using going to be affected by the cab you're running through? I thought that is the reason for using FRFR's, so the profile sounds like the original.
A guitar cab will naturally color the profile you're using while an FRFR cab (by definition) shouldn't.
Thanks to the cabdriver feature (introduced in firmware 1.5) you can still get the core of different profiles when using a guitar cab though.
This is a feature that is very unique to the the KPA and works great.