Are you trying to save money or just get the best board?
The KT600 is a good chipset, and nearly matches Nforce benchmarks, but I am unsure of its overclocking capabilities,but they should be decent.
The NF-7 is the king for Overclocking as of the moment, with modifications it can reach a 500FSB, and 440FSB out of the box
Are you planning the regular NF-7 Or the NF-7S with Sata drive?
If you can afford it, get the Sata!
Hands down everyone here will say NF-7, someone even posted a poll