Unsure what monitor / rez you are running. Also unsure what quality settings you like to use.
If you are running a 1280x1024 (or less) monitor then it's a fine used buy for $100-$120. If your monitor Rez is higher. Say 1680x1050 or higher ... you'd want to evaluate based on the games you play. But generally for a 1680x1050 or higher I recommend a 3850, 3870, or 8800 series.
Again though I don't know what you play or the quality settings you like, so I don't know if you can "get away" with the 8600GTS.