Hi. I ordered nearly the same componants as you a couple of days ago and weeks of research for my new rig! I decided not to go for Sli as i heard from many reviews that it's a bit unstable at times...I don't really know how factual that is? Also, just how functional it is, it all sounds overly complicated as it's all relatively new technology. Instead i ordered an Asus A8N-E seen here: http://www.microdirect.co.uk/Product...91&GroupID=526
I don't know how much cash you have to spend, but getting a different board, which was as good as the same just minus SLi saved me a wad of cash which i put to getting a 3500+ instead of a 3200+ and a 6600GT instead of a 6600 (Gainward GF 6600GT) which is apparently a lot better.
This was all based on the fact that i didn't wholy trust SLi because it's so new and it's also very very expensive and i'd likely never use it.
I don't know if you're in the same position but cutting SLi can save a lot of money if you're not likely to use it.
Afterall, if you get a normal mobo and a 6600GT you only need another 6600GT and a Sli-compatible board if you change your mind when they're cheaper in the future.