1. A video card that has dual DVI/VGA outputs (which most do).
2. I would go with Asus, they defiantly have more experience in the motherboard field than EVGA (even though I love EVGA videocards).
3. RAM by itself really doesn't have much performance advantage than any other RAM at the same speed. I'm sure that RAM is fine.
4. Case fans are case fans, not much of a difference between different brands. The only things really to think about are: size (normally 80mm or 120mm), airflow, and noise level.
5. Depends on what you mean by performance boost. If you mean like FPS then no, if your talking about boot/loading times then yes. Personally I recommend against it, as not only the chance of a drive failure increases, if one goes out then other one goes out. I single 10K RPM hard drive (like a WD Raptor) will be fine, I guess if you have the money for it. I really don't see that much of an advantage worth the price over a standard 7.2K RPM hard drive.