i was afriad u would ask that, probly run system diagnostics and make sure everything else is clicking in place, is the ram all acounted for, is the cpu running at reasonable temp, etc
if everything else seems fine i would get the new card
Well if you were looking for a reference for prices for GPU's, PC Case Gear has a good website and usually their one of the cheapest (give or take $20).
Here is the website if you wanted to check it out: PCCG
You can pickup a 7870 for around $250 - $280 and shipping shouldn't be too expensive.