Hm. Ill think this over.
Great MB, i belive there is a asus p5q+e8500 deal,
http://www.newegg.com/Product/Produc...Size=10&page=1
Dont attempt to OC a Proc on stock cooling. I personally would get a TRUE or Tuniq tower, but those are 2x the cost of your current rig.
The antec 900 is a great case for a bugdet build, it will make you very happy.
I would keep 2 of your current Hd's, put them in raid, and buy a 1tb for backup/storage.