Phenom II X4 965 @ 3.8 / 2.7
It's just a year old, but the Sandy Bridge review did have me thinking of an upgrade. If the stock Intel cooler can do 4.4, then decent aftermarket should give a bit more at least. And since 1156 compatible coolers are compatible with the new boards for SB, that makes it even better as my Hyper212+ should do the job nicely on a 2500K if I do get one.
Since I am in no hurry, though, I'll let the Z68 boards arrive first and see what AMD delivers with Bulldozer before touching my main rig, especially because I am not yet doing anything that demands much more than what my 965 BE can handle.