We put a fxf hd4770 gpu in killer91's computer a few months back. If I remember right, with v-sync off his fps went up over 1000 when he look up in the sky. For comparison bravoa8 has a evga gtx260, his fps were only around 700 looking up at clear sky. I have a visiontech hd4650, my fps were 258. My card is only one that was overclocked at the time.
That 4770 is an awesome card for the money. Think I gave $104 for it at Amazon.
Had all the eye candy turned off w/1024 resolution.