That's a tough question. In my case I had the 633T for LR and the 533VAC for C. I could tell a difference in tonal balance, bass response, and in general it just felt like the center was "too small" compared to the sound I was getting from the 633T's. I've recently received my 634VAC and it fits perfectly. I love it.
You might try calling Aperion (assuming they haven't shipped yet) and see what they recommend -- they might have run into this with previous customers. I would hazard a guess that the suggestion would be to go with the 632 (since you can't fit the 533VAC into your setup). Will the 632 fit?
At least Aperion has a great trade up policy. If you get the 532 and find you don't like it you can ship it back and order the 632.
Let us know what you think and do.
(And of course give them about 50+ hours of break-in time before doing comparisons
).
Mike