I would get an E4, that's a Manchester with the second core disabled, it will have a lot larger surface area with the IHS, thus in theory should run cooler. It also runs at 1.3-1.35v instead of the regular A64s 1.35-1.4v.
Moto: No point in getting such an expensive chip, when you can get a cheap one, and just run it at stock speed and undervolt.