3. I'm not sure the reason. But according to this chart I found elsewhere in the forum... you should go with Nvidia
4. As for Z68.... The biggest benefit I am aware of (and I'm a newb so don't rely only on this) is the ability to do SSD caching. By the looks of it... I think you're okay with the harddrive choice for doing SSD caching. What I've heard is if you decide to pursue SSD caching check that your Read is ardound 200MB/s and your write is around 100MB/s. But hey the Asus Z68-Pro is sold out on Newegg if that's where you wanted to buy from.