For 3,000$ you might as well max it out. Unless your trying to go as low as you can. Heres what I think.
Keep that same motherboard , the 780i
Get three of these 9800 gtx's cards and run them in tri sli
http://www.tigerdirect.com/applicati...445&CatId=3670
Then a 1kw psu
http://www.newegg.com/Product/Produc...82E16817153054
And I think you should go for a core two extreme.