No, I plug into my Marshall with my LP it sounds excellent. I don't have to wait months for it to sound good. If someone tries a £1450 piece of gear and it doesn't sound satisfactory to them, in my experience it doesn't get better. I'm happy to know what people are doing, to get their Kempers sounding the way they want them.
You may plug into an expensive Marshall and not like it. Someone telling you to be patient is a load of drivel, unless they suggest how you can get the sound your looking for with the gear your using.
So what are you actually doing with the Kemper to make it sound better? Apart from patience, what's your actual technique?
Have you stuck a mic in from of this marshall, then gone to a room where you are only listening to that sound via monitors and it still sounds just like you want to hear (unlike the Kemper)? If so then i would either, profile your Marshall (as others have said), or get a load box/IR loader and call it a day. You may not be at all happy with that either if you are used to sitting in the room with your amp through your cab and move to mic'ed sound (Kemper/IR) and monitors. You've stated that you have a lot of studio experience so you probably know this, just throwing it out there.
I go back and forth from the fence on keeping/selling the kemper weekly for a few reasons, but its a personal battle that some need to fight. Others love it all the time, i love it 51% of the time. I think the new Reverbs might bump it to 60%
will listen to the clip...i also recommend Soundcloud for free/easy clip posting.