If performance is really that important, just go for the i7 3930K. 6C-12T, so a lot more processing power than the E5 1620. A lot more expensive too (if the 1620 ever becomes available in a boxed form), but if the processing power is truly needed, that's the way to go.
The need for ECC RAM isn't really an issue, as you're not talking about a server, and 64GB is the max amount on the 3930K, which should be plenty for anything you're doing.