So TGP has a thread where a guy was asking about using a Kemper instead of a guitar amp through a 4x12. All sorts of advice came in, I thought I'd actually mention something that worked for me and support it with a clip.
If you're going to use a 4x12 with your Kemper, your best bet in my opinion is to create or use profiles that have been pulled with a hotplate or some sort of load device that provides a line out. Why? Because this gives you the tone of the amp (including the power tubes, since it is coming off the speaker out) and doesn't have any of the microphone coloration.
I'm NOT saying you can't use a regular profile successfully, this is just in my opinion the best way to do this, for use with a 4x12 cab ONLY. If you wanted to use it in conjunction with direct outs for say FOH, you'll have to mix and match cabs and it may or may not work well. But for use with a 4x12 and a 'in the room amp sound' this is going to be hard to beat.
Here's a clip I did earlier today with a hotplate, Soldano, marshall cab, rocktron velocity power amp and a Zoom Q3HD:
I know it's not exact, had trouble matching the volume levels from memory between the soldano and the power amp, but for a cheap power amp I think it's easily in the ballpark and a few tweaks to the global EQ and you'd be there.