That's a great clocking board for any S939 chip. With X2s, probably your most sensible options are to go for the 3800, with 2x 512kb cache or the 4400, with 2x1mb cache. The others simply raise the stock fsb while keeping the cache the same, so it's a waste of money if you're going to be clocking, as you'll be going way above the stock clocks of the intermediate chips anyway. I don't think the intermediate chips clock as well as either of these either - this is certainly true of the 3800 v. 4200, anyway.
A dual core opty would do nicely too, though I don't know too much about clocking those.
Hope that helps.