If you're going to be overclocking, you'd be better off going with memory that's faster than the base speed. In your case, you'd move from DDR333 to DDR400 (PC3200) in order to get better overclocking stability (else your 333 memory is running at, say, 380 or something, which leads to problems). This is, of course, unless you mess around with how the timings are set up (getting a 5:4 ratio or something) which can result in the corret speeds, but then your RAM will be running out of sync with the chip, and so performance will decrease.
As far as the CPUs, I haven't heard too much about the overclockability of either one, as most OC'ers seem to prefer going with the Barton 2500 and pumping that up. Generally, the higher processor speed within the same core results in less of an overclocking ability (which says that it's easier to overclock the Barton 2500 than the Barton 3200).
For the mobo, I'm going with the A7N8X Dlx, but that's just me. I like to have the "upper" motherboards available, but I don't know why the nf7-s wouldn't work unless it doesn't support DDR400 (and therefore the faster speeds).
Hope this helps. 🙂
