The 2Ce Signature is a step up from the 2Ce (especially if is an older 2Ce that used the 3/4" tweeter instead of the 1" model) It is more open through the mids.
I agree with Scott that the step up to the 3A Signature is a pretty big jump from the 2Ce or the 2Ce Sig.)
The footprint of the 3A Sig is about the same as the 2Ce. It is about 10" taller. I feel that if the 2Ce worked in your room then the 3A Sig will also. However, the 3A Sig is more revealing of sources and electronics. Make sure you're in good shape there. Otherwise, you may not hear the real differences.