Ok your PS should be fine then.
As for the vid card - heck the 4870 is a sweet card - x2 you really shouldn't need to upgrade for a while. But its your dough.
If you go with this board - realize that its BUILT for SLI - meaning you will want to go Nvidia with graphix as you can add in another card later if you want. When you get a mb - you need to know if your going to sli/crossfire or not.
As for overclocking - I don't do it but the ASUS generally is thought highly of - and the mb line in particular (gamer series) is well spoken about.
