R u 2,3,4 or 5 boxing.
the build U have now will be able to 2 or 3 box with medium to high, very low fps with 4 or more

Rosewill is not a very good PS, I will go with Corsair 550
http://www.newegg.com/Product/Produc...82E16817139004

U will be limiting yourself with a mb with only 2 dimm socket this will be better
http://www.newegg.com/Product/Produc...82E16813128380
my friend is using this with Windows 7 and was able to use 2 different video card with 4 monitors. ( I am trying talk him into letting me load wow on his pc and try to 5 box of it)

I will get the faster memory ddr 1066, it cost about the same and give u more room if u want to OC
http://www.newegg.com/Product/Produc...82E16820231166

I will also buy a CPU cooler, I hate the way intel design, it is a pain to get all 4 pins in and make sure they still in. I will get a cpu with a back plate like this
http://www.newegg.com/Product/Produc...82E16835118003