thanks for your recommendations
i mentioned that i would like to have a good graphics to play some latest games so i went ahead with 4850
here are my upgrades
WD 640GB Caviar 7200RPM SATA 3.5
SAPPHIRE Radeon HD 4850 512MB PCIE
CORSAIR 4GBKIT (2X2GB) 800MHZ NON ECC
GIGABYTE GA-73PVM-S2H - NVIDIA GeForce 7100 Chipset - µATX
Intel Core 2 Quad Q6600 - 2.4 GHz, cache L2 8 MB Socket 775
total was 550
-100 (current agp card which will be sold
=450 Which seems like a good upgrade.
will post how the upgrade works out.