building a computer

I'm more or less new to computers and own a dell atm. =(
Here is the parts list that I made earlier:
2x 17inch monitors, http://www.newegg.com/Product/Product.asp?Item=N82E16824009036
case: http://www.newegg.com/Product/Product.asp?Item=N82E16811156177
extra fan: http://www.newegg.com/Product/Product.asp?Item=N82E16835129243
motherboard: http://www.newegg.com/Product/Product.asp?Item=N82E16813131540
memory: http://www.newegg.com/Product/Product.asp?Item=N82E16820145587
2x sli 7800gt http://www.newegg.com/Product/Product.asp?Item=N82E16814121004
cpu http://www.newegg.com/Product/Product.asp?Item=N82E16819103603
soundcard: http://www.newegg.com/Product/Product.asp?Item=N82E16829102003

The prices add up to about 1500 with the two monitors, I have speakers, keyboard, and a mouse.

Including things like wires and such, what all do I need to consider/know about/buy along with all this. Or maybe any suggestions to replace some of these parts with similar priced products that might perform better with that set up?

Any help appreciated.

>>16
They do NOT cost less than most graphics cards. At $290 US for the cheapest ones on newegg, most cards cost less than the 7900GT. Quite a bit less. An X1900XTX is about $480US. So one 7900gt is cheaper than one X1900XTX, but 2 certainly are NOT. Unless you mean two X1900XTX in crossfire, which should be faster than your SLI if one is only 20% slower.