Thanks so much to everyone for all the great advice. I can see there are many possible solutions.
I think I'm headed toward a setup with FRFRs to get the full potential of the Kemper. (RIP my 42 year old Marshall cab.) I'm taking the advice of many that getting the power amp is worth it even if I don't use it often.
Stereo. I don't have any aspirations of playing outside my little rehearsal space so I may still go the stereo route. I realize that means buying a second power amp if my old Peavey Classic 50/50 doesn't work well. I also have to decide on waiting for a Kabinet, building cabinets with Kones, or buying third party FRFRs. I saw an interesting stereo setup using a Camplifier so I'm wondering if that would be a good solution. I'll have to do a little more research.
Thanks again for all the help!