I'm the guitar player for a few bands, and more often than not I'm also the soundman for an 8 piece band with a 3 piece horn section (while playing guitar and singing... I'm busy.)
And this, I think, has given me a perspective that I haven't really seen discussed which is the idea of using various rigs with radically different sounds at a live gig.
It's one thing to use an AC30 for clean tones and a Marshall for dirty, but it's a soundman's nightmare when you go from a nice warm vintage marshall plexi on one tune to a scooped Rectifier on the next. You're likely to wonder where the guitar went because the engineer EQ'd you for a Marshall and then you switched to the exact opposite.
I've learned to keep my rigs in the same family by and large. My clean tones are mostly Fender-ish and my dirty tones are more Marshally than anything else (even though I'm not using a Marshall.) But I've found that if I switch over to the EVH it sounds really bright and harsh with no meat because it's considerably brighter than the Marshall with considerably less mids.
Once I've "carved a space" for a Marshally tone in my EQ with the other instruments and singers, the EVH tone doesn't fit in that same space and if I want to use that sound I need to adjust the EQ of other instruments in the mix to make room.
Just something I've learned over the past couple of years gigging with the KPA that might help someone just getting on with it.