Weakest Link?

I am buying a pc to build. I have a little room to move, $$$ wise, so what do you think I could upgrade?
AMD4200+ 2GBWintec RAM HIS Radeon X1950 Pro plus my Case and my Rosewill 500W PSU?

Case: http://www.newegg.com/Product/Product.asp?item=N82E16811147001   How many fans should I add?

PSU: http://www.newegg.com/Product/Product.asp?item=N82E16817182016  

Also, how much should I expect a local place to build this? $200?

Windsor is 90nm

Brisbane is 65 nm

so, what does it mean? windsor is significantly faster than the other?CMX115