I I'd like to be in that situation.
My "problem" is the IEM always sound different. I use my own earphones, and we ask for the IEM system in our Rider. And that's it: the sound is always different. Sometimes it's incredibly beautiful (if you can say a raw electric guitar rock sound is incredibly beautiful), sometimes it's not that good. Sometimes it's bad. Always our own sound man, too.
Yes, yes, different gear, different sound, but I've played live with IEMs more than 200 times and I'm sure I haven't used more than a few IEM different systems/brands. AND for little private gigs, I use my (cheap) system. And it also changes depending on, I guess, the rest of the gear.
So if I don't feel comfortable enough, I try a little EQing. But as long as I know the PA sound is great, I'll be OK (if things are not too bad onstage).
Same here...its nothing to do with the KPA, in fact the KPA and other digital stuff takes some variation out of the equation ( tube temp, mike placement, type of mike etc).