Well, it didn't take long; I scored a used LX center and set up all 3 in the living room at the same time. I'm happy I just went straight for the LX. If I had bought the 200 / 340 setup, even if it was 95% as good, I would've always wondered what I was missing.
The LX's sound incredible. My wife and I binged "A Spy Among Friends" across the day I switched over, so it was some good comparison. Dialog is so much clearer and I can really hear nuance of the rooms around it in a way I never could before. I think the center was really the weak point of my old paradigm system. I also watched Arrival, and the bass impact of the LX is just incredible for a bookshelf speaker. My wife commented that she felt the impact in the bedroom above the living room. I'll definitely have to find a way to set some bass rolloff if I watch anything after she's actually trying to sleep.
Given how good thing are already, I decided to just finish off the system. So, an Onkyo TX-7100r from Black Friday sale arrived yesterday, and I placed an order with Ascend for a pair of HTM-200 to replace the surrounds and a Rhythmik L12. I ran a quick Dirac Live cal last night with only a few points and the software is so much nicer than the ancient audyssey I had before. No real comment on the sound yet; only had a little time last night. Once the rest arrives, I'll run a real calibration and dial things in.
I think once that order arrives, this is an endgame setup for me unless I ever have a dedicated room in the future. Thanks to everyone who commented, especially SunByrne for the LX suggestion.