Ding ding ding, we have a winner!
After thinking it through I decided to go with a "regular" (vice single-stud) mount. And on a whim I checked craigslist -- lo and behold a guy was selling a top of the line OmniMount UCL-X for $155. Talked him down to $125 and walked away with it.
Got it mounted up -- just need to order some longer HDMI cables so I can tuck them along the mount and make the TV truly float.
Thoughts? You can see that the mount is offset from the center of the TV. Plus, I couldn't hit a stud with the right-edge mounting holes so I put two lags through the adjustment track of the mount. Not the way it's supposed to work, but certainly does the job.
From above:
And here's the old setup with the basic TV stand (which didn't leave enough room for the center channel).