Upgrade to High Performance Gaming PC

My PC Configuration.

Intel Core 2 Duo E7200 @ 2.53GHz
Intel DG35EC (LGA 775)
2.00 GB DDR2
250 GB Seagate ST3250310AS (SATA)
22" LCD Monitor
450 Watts PSU

I wanna Upgrade to High Performance Gaming PC with Super Frame Rates
at Higher Resolutions with Ultra Settings on a Single Monitor.

Which Graphics Card had Good Value for Money ?
-NVIDIA GeForce GTX 680/670/660
-AMD Radeon HD 7970/7950/7850
What Other Components should I upgrade ?