Impressive system. Should be wowing you regularly. What are your cables? Based on what you've spent so far I'm sure they are also top notch. But they can be a "choke point" as it were, especially in a system like yours, even if they're good but are a mis-match. Still, something isn't right. I get room issues. I live with room issues. But even my system, which is way below yours, delivers clear and lively mids and lower mids, good separation and is very engaging musically. I'm thinking maybe your crossover is set way too high. I'd try turning the subs off all together. Does some of that airyness your looking for show up? If so, then listen without the subs for few days until your ears become accustomed to the sound and then ease the subs back in until they just barely touch the lower mids. Listen for a while to again let your ears become accustomed before adding more.
The only other problem I could think is there is a hardware issue. It'd be in either your pre-amp or crossover. A tube that works but is actually failing, a weak cap or leaky diode somewhere. Devilish to track down. Maybe test with the crossover removed? Can you swap in a different pre just to see what happens? Even with a lousy listening space, your system should be singing. Something's not right.

