Vandersteen

IMHO, not enough to justify the price increase. YMMV!

In this particular instance you would be wasting your money to allocate it toward electronics when for $2K you could move from the 2CE to the 3A. That from a former 2CE owner. If I were in your position and could afford the 3A I wouldn't dream of opting for the 2CE. 

Very few manufacturers in the industry give you more for your dollar than Vandersteen. When setting up a rig that will be around for a while it's penny wise and pound foolish to opt for the lesser speaker, especially when Vandersteen gives so much for the price. 

It would take a significant investment in fine gear and cables, maybe on the order of an additional $5-10K in components, and perhaps even more, to have a 2CE outplay a 3A. I'll keep the ball rolling; YMMV

@bdunne,
I assume you are considering buying used. So, cost differential would be minimal.
In any case, the biggest difference between the two models would be that the 3a sigs would have greater bass capabilities.
If you love Vandies like I do, then the next best upgrade would be to add a pair of 2w(q) subs which will bring you almost equal to a pair of 3a sigs.
(I upgraded from the 3a sigs to a pair of Treo's and use a pair of 2w subs. Mr. V. says it gets me to 90% or a pair of Quatro's-These are non-CT versions). So, if you want to upgrade in the future, you can still keep the subs.-Which, by the way, are the best subs I have ever used, despite not having a 'q' adjustment.
One of the things I didn't like about the 3a sigs was the footprint. The Sound Anchor stuck out like a sore thumb and made positioning much more difficult that the 2's and Hence, my move to the Treo's.
You should PM John Rutan at audioconnection (his store and Agon ID). He can give you the best information. And, he's a great guy, too.
Bob