The obvious answer is that any DDR400-rated memory should get your to 3200+ level.
You don't say what motherboard you have. I think it's VERY important to check forums for that motherboard to see which make of memory is most compatible with that motherboard, particularly if you wish to o/c above 3200+ level.
I've always been a Corsair fan, but had disappointing o/c results with my 8RDA+, which seems to like any DDRAM with Winbond chips.
Hope this helps!