Best ram performance/value atm

[semisonic9]

Digging through my old wishlists in preperation for my build next month, and just wondering what some good ram would be.

The build is:
q9450
DFI Lanparty x48
ATI 4870
640gb WD hd
PC PnC 610 wor 750w
Cosmos S

A) What kind of ram (DDR2, DDR3) and what speeds are appropriate and cost-effective for this build?

B) And...if I want to OC and watercool? Does the answer to A) change?

Thanks!

~S