Hi,
- Mic up your amp the way you would play it live in another room and send the sound to your PA
- Dial in the sound until you are happy with what your hear
- Add the KPA to the signal path, it should not change anything in the perceived sound
- Profile your amp and A/B with the real amp during the profiling process
- Once you‘re happy with the result you should be able to get the same sound out of the KPA that you got with your amp
- If you still do not like the sound then it is not about the KPA
- If you do, you can profile various settings of your amp
- Then, go check other rigs on the Rig Exchange
This is the way I did it and maybe an easier starting point than digging through the overwhelming amount of available rigs.
Don‘t blame the messenger (in this case: KPA)! 
