I would go for the 3.0E. Should hit 4GHz easy on water cooling. Air...it'll hit 4Ghz but isn't stable, at least in my experience. Also, not much difference between the 3.0, 3.2, 3.4 as far as oc'ing goes...small gains, but not much.
Besides, why spend the extra two bills on another 478 chip when the conroe is due out here pretty quick. It'll take these 478's and literally flush them down the toilet. Just my two cents anyway.