I've been doing my research for who knows how long and I think you'd be happy with the 1.5ghz C7 processor. The other board will be upgradeable in the future, but honestly how many people actually upgrade the processor down the road? You'll probably want a newer board with better memory controller or some other feature that you won't have now when the time to upgrade comes along.
I'm waiting a little longer because there is a 2.0ghz version of the Jetway on it's way. That will be a little more expensive so we'll have to see if the extra expense is worth it. Regardless of what any of us buy, there will always be something cheaper and faster next week.
Here's the 2.0ghz board, but it's a little pricey right now:
279 for 2.0ghz or 150 for 1.5ghz is a tough choice. Hopefully sometime after the holidays and when a few other manufacturers can get a 2.0 board out the price will come down to 200-225 range then I'd consider that a good deal.