I would suggest:
1) Don't buy anything new yet - you need to trace the problem, which could even be the KPA doesn't sound good to you. I doubt that is the case but it is possible.
2) How "bad" is it? When you say they all sound the same, I presume you don't mean there is no difference between a clean AC30 sound and a Mesa boogie on full tilt? Sound clips will help.
3) Is it very similar through Headphones? Can you borrow some reasonable ones just to at least get a baseline? That totally rules out the QSC's.
4) Have you got access to any other signal chain e.g. through a PA just to try?
I think its unlikely its the QSC's as they are reasonable speakers. Not everyone likes FRFR but you should get the opposite, its too transparent and you hear all the changes but sounds less amp in the room like. You will never mimic the sounds on line as there are so many other factors, but you should be able to get really good sounds if not great sounds. I can;t think of anything obvious except a low pass filter or something global but no obvious candidates...
Not everyone gets the " revelation" of sound. I didn't myself, it took me 12 -18 months journey to go from OK sound to good sound to great sound. But it never sounded bad so hence the level of disappointment is important.
However, my constraint was a real cab and duff profiles which only showed up when using FRFR ( so the opposite of your problem).
I appreciate the suggestions. You are correct about me noticing a difference between clean and distorted/gained out profiles. Its really just the inability to hear any major differences in similar profiles and the respective amps/cabinets characteristics for each profile. For example a clean fender profile on my kemper sounds the same to me as a clean marshall profile. Both paid for as well. I have seen a thread where someone mentioned turning off pure cab, but i didnt notice much of a difference that way either. I even changed the settings on my QSC to guitar settings, to see if that would make a difference. I think thats what made me believe that I should just invest in a kemper kone to dial in my tones, and then maybe i would really hear the difference, and it would be portrayed better in a PA. Not sure if thats the best way to look at it, but I really dont want to give up on the kemper.