@Arclight
The 8800gt is not really a lot faster than a hd3870. the diffference is only about 15%!
I do recommend Ati hd 4870/4890 1Gb or Nvidia gtx260/275.
They are about 70% to 100% faster than a hd3870.
But you probaby need a new power supply like the other said.
About 500W and 30A on the 12V rail.
Also I recommend to overclock your CPU or get a new one with about 3GHz.
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