I need advice on which cpu to choose to go into my new build

So far:

Buffalo FireStix 2GB (2 x 1 GB) DDR2 800 PC2-6400 SDRAM
EVGA 8800GTS Superclocked 640MB
ASUS P5W DH Deluxe Motherboard

Which cpu would be best to go with that lot.

Get a normal intel E6300 with L2 Cache - 2 MB and overclock or get the new version E6320 which has L2 Cache - 4 MB.

Or get the E6420 which ive heard is a better chip again. Will the L2 Cache - 4 MB on the new version make a difference.

Any help please

If you can swing it, go for the E6600. It's only 230 @ newe.. now with no rebate. You won't be sorry!

Ok thanks
Is there a certain branch code i should be looking out for when buying one?
Im talking about the E6420

If i was to buy one from ebay boxed and sealed would i be able to ask the seller the branch code wouldnt it be on the box?