What does you current system not do that you would like it to do? What do you use it for primariliy?
If it's for gaming, then you'll probably want to upgrade the video card (though that depends on which games, and how high you want the settings/resolution).
soory i forgot to tell that my purpose is gaming and i played crysis , dead space without any interruption on full hd res (high).u know i bought this rig nearly ten months ago for $1150 and at the same time new processers like cor i3 i5 i7 were introduced and if i hav to upgrade this sys to core i5 or i7 i hav to change the whole system into ddr3 and that will cause a huge loss thats why i want to spend money now becuz i hav no chance of changing it into ddr3 about next 2 years because next year im going to buy a laptop need for engg. university work.
actually the pc is running every game smoothly like crysis and other games cod mod warefare2 but some games like spinters cell conviction just crashes out at the start when the sponsers r displaying their names i dont know why so tell me weather i should do an sli configuration of gts 250 or i should replace it with ati radeon 5850 or any other sugg. by u. remember that the upgradation should last at least 1 and a half years. now ur call.
also remember that im from pakistan and option r limited and here their r no monthly payment packages and the price is also high from other parts of world due to taxes. and the brands available in pakistan r xfx evga cooler master corsair asus HIs and no antec