OK... so turning off res, thump and decay in the cab DEP makes a huge, huge, huge difference. Suddenly my amp EQ settings actually do what they're supposed to do. I can set them to 50 to begin with and dial in the tone from there instead of using all possible settings to dial back the bass and treble monster. Still probably not as good as some of those sweet third party IRs, but good enough to continue using it instead of dropping a bunch of money on something new.
I'm surprised to find (now that I can hear what the models are actually supposed to sound like) that I prefer the sound of the Hiwatt driven with Boost Comp and Line 6 Drive to achieve an 80's hard rock tone over going with one of the high gain models, but this actually works out pretty well since turning effects on and off has no lag while changing patches does have lag.
Not sure how I missed the intel on the cab DEP settings over the five years or so that I've had my POD HD, since I'm always searching for ways to get better sounds out of it, but glad I finally have that worked out.
Thanks, all, for your comments. I think I can easily gig with my new band using my current Hiwatt patch.