Dell cpu/motherboard/memory speeds

I'm looking at getting one of the following cpus in my new dell 530.
Which memory speeds would you recommend for each of the following and why:

Intel® Core™2 Duo Processor E7200 (3MB L2 Cache,2.53GHz,1066 FSB)

Intel® Core™2 Duo Processor E8300 (6MB L2 Cache,2.83GHz,1333FSB)

Intel Core 2 Quad Processor Q6600 (8MB L2 cache,2.4GHz,1066FSB)



Thanks!