I think I'd personally go for one of these:
I read a couple reviews where these sticks got to DDR500, I posted one earlier
ocz makes great RAM, the platinum line are made specifically for overclockers. while the entry levels don't oc near as well as the better ones, you should still be able to get in the DDR440-500 range
I'd get one of those two kits for your price range.
if you can squeeze a bit more out then I'd go for one of these two kits:
it looks like people are getting DDR550 or so with those kits... so if you're planning to OC they might be well worth the extra $20. or so.
one thing to keep in mind... while high performance RAM is always best and keeping a 1:1 ratio will most times give you the best performance if you do get a kit that just can't keep up w/ your cpu you can run it on a dividor.