folding could care less how much cache you have, but it certainly loves MHZ
i'd say get the newcastle, not only for the faster default clock for folding, but the newcastles are looking to be the better overclocker of the two cores. Silver has his newcastle 3000+ at 2.75ghz on plain water cooling
I plan on getting a Clawhammer for my DAW I am building that will also be folding. This will be the first rig I have built where silence is more important than the OC. I hope to still OC a little bit but I gotta find a silent heatsink first. How's the stocker? Still the same as the AMD XP series?