After living with it for a couple days, the center jumps out a lot more. I'm really kind of surprised. Didn't think raising it a foot would make such a difference. But it's definitely something I've noticed.
Will probably break out the leveling gear and retune all the speakers. Never did it after getting the stands on the surrounds, so after this, I'm definitely due.
Whenever a 6C is in my future, I'll probably swap the two shelves under the TV. While the top shelf is about 3/4" too narrow, and probably wouldn't be a big deal to hold it, I don't need a larger shelf for just my PS3, so I can put the new center on the larger shelf and have more piece of mind. They're both rated at 50lbs (6C weighs 37 or 39, I think), so either would probably work.