That's awesome for the price. If you OC the CPU it will be better than any budget build you can put together. You can re-use the 1TB HD, PSU: 1200w quiet quad rail, and Case: coolermaster 932 haf case, and optical drives even if you upgrade everything else so just those are worth the cost. You can either upgrade the RAM to 8GB (though DDR2 is overpriced right now) or just upgrade the CPU, motherboard, and RAM when you feel you need more power.
if it were me i would keep the PSU, HDD, gpus (in sli that is still pretty powerful) and case. sell the rest and use my all my spare cash to try and put together a 2500k system on a cheap but decent board I.E. asrock z68 gen3