Having re-read the previous responses, I will say this: The Kemper is an amazing piece of gear - I will be testing it severely during the next two weeks. I frankly don't care what the fanbois think, nor the hopeless critiques - I just want to see what it can do tonally.
You can profile with your HC between the mic/micpreamp and KPA in case you like to get rid of unwanted fizz.
I for myself found that I get about the same fizz as the mic in front of the real amp produces - and that is what I want.
Btw. it's possible to add an EQ block in 'X' in order to get rid of any unwanted fizz or woofy low end.
When my profiles do not sound great - then I try not to fix it later but to choose another microphone or mic position ...
Regarding fizz, I have always felt most guitar amps sounded too fizzy for distortion until the master volume was cranked high (unless additional processing was involved). Ironically, I haven't been able to get serious with my KPA yet because it arrived during our concerts in Hawaii, and as soon as I got home I had to build many of 'the boxes that must remain unnamed' 
Gotta wait for the wife to run errands before I can do any serious profiling however - too much noise! 
The thing I noticed is a tendency for the Kemper profiling to add a bit of upper mids, while loosing a bit of the ultra lows, but it wasn't a huge thing to make up for. I feel the quality of onboard effects is very good, although it would be nice to have a broader selection. The Reverb in particular is quite good - very natural and full-sounding.
