That makes sense--it's set up to use like a real rig, and the deeper I get in the rabbit hole, the more I see that things interact as they do in the real world. While I still don't understand the problem I was having, the more I read here and the more I think about it, boosting at the cab was a weird idea. It was convenient because I was using A/B to trigger both pre- and post-amp boosts.
I have tested each of Leon's ideas and find I like the PEQ best--for the reason you've stated...it seems to really make a solo sit on top of the mix...thusfar only at home with mp3 for "band mix." With my FX8 and Dirty Shirley, I was using a filter block, but, perhaps because I'm listening more critically in earbuds, I don't like how woofy that gets. With the PEQ I'm boosting 2K by 2dB and blocking below 80Hz, while setting the output at +2dB. That gives the same volume as 3dB on a filter, but cuts much better.
Unfortunately I don't have a gig now until early January
but will try it with this soundman then.