I know I could go cheaper, but don't want complete outdating in 2 years

Right now I'm using 3 GHZ P4, 2GB RAM, 80GB HDD and some budget Geforce, not even sure what.

Here is my tenative system....... I'm not to sure on modern hardware, haven't caught up in a long long time.

Rosewill Challenger Black Gaming ATX Mid-Tower Case
http://www.newegg.com/Product/Produc...82E16811147153
Western Digital Caviar Black WD6401AALS 640GB 7200 RPM 32MB Cache SATA 3.0Gb/s 3.5" Internal Hard Drive