Here is a sample config...
As for your questions -
SLI - It is a Nvidia specific name for a technology that enables to run 2 similar video cards together to gain more performance
Crossfire - ATI specific name for the same...
2. Overclocking - It is increasing the clock speed of the CPU...
And I dont think you would need the ASUS Deluxe board...Instead save money and get the ASUS PRO...and also you can go Crossfire with this PC as the PSU has enough power to handle 2x HD 5850s and also the mobo supports Crossfire...
1. CPU + Mobo
i7 860 + ASUS P7P55D-E PROhttp://www.newegg.com/Product/ComboDealDetails.aspx?ItemList=Combo.354337
2. RAM -
G.SKILL Ripjaws Series 4GB (2 x 2GB)http://www.newegg.com/Product/Product.aspx?Item=N82E16820231277
3. HDD -
Samsung F3 1TBhttp://www.newegg.com/Product/Product.aspx?Item=N82E16822152185
4. Graphics card
HD 5850 - Assuming you would like to game at 1080p, the HD 5850 will better suit...http://www.newegg.com/Product/Product.aspx?Item=N82E16814102884
5. CASE + PSU
Antec 300 Illusion + Antec EA 750Whttp://www.newegg.com/Product/ComboDealDetails.aspx?ItemList=Combo.345229
Total - $1109