Definately 4400+ (IMO) I've got mine at 2.5Ghz no problem.
Correct me if I'm wrong (as if i had to ask) but isn't it just exactly the same piece of silicon but with one highe multiplier unlocked?
Buy something else with the $300 you save, like, say, awesome cooling for it, that'll help you achieve a good overclock. Get an OEM version without a HSF and box etc, then get a good CPU cooler and some Artic Silver 5. There's doubtless many threads about good X2 coolers.