I'll make a suggestion. Forget about the p/u, and just get the best sound you can unamped. That way, if you were using just a mic for example, you would be getting a happenin' sound. Maybe you are there already. If so, cool.
Then ... Start fiddling with how your Rev Solo fits in the slot. Or try different amp settings ... or different pickups (many of us have), different amps, or maybe preamps. But keep the pizz approach as constant as you can. Find the equipment and settings that work best w/ the way you play your bass unamped. Don't adjust how you play to make the p/u sound better.
Unfortunately, this is something I am guilty of. I use different right hand technique when I use only a p/u vs. no amp or just a mic. I get lazy using a pickup. In fact, when I really dig in like I would w/ no amp, the p/u I use starts to sound pretty ratty. So until I make some changes, I've got two techniques to keep up with. But I know it really shouldn't be so.
Mid-range is key like you said. Cutting it may sound more natural at home, but boosting may help you sit in the mix better live. It's an overused term too that means different things to different people / ears. But you are right, it is critical to getting a realistic amplified tone for bass, for helping you hear yourself, and helping others hear you. If you can't adjust the frequency like with a parametric, then all you've got is boost and cut. What works best might change somewhat from room to room and from group to group.
Sounds cliche, and I am admittedly no superstar, but except for the HPF, I run my EQ flat and try to get the tone from my hands. Like Uncletoad said, where the speaker is placed is also key, and will vary from room to room. [ Edit: Speakers close to walls and corners emphasize depth & low end IME. Moving away from same thins out the sound. ]
Just gotta keep experimentin'. We all do pretty much ...
