I been using a Sapphire 5870 for 2 years now and debating if I should upgrade. I can get about $170ish for my old card and should I even bother upgrading or just stick with my 5870.
1. sell it on ebay/amazon and get a gtx 580 &590.
2. stick with the card and wait til the "actual" upgrade
3. get yourself a crossfire setup with another 5870
4. if you don't play game or folding/ decode then that 5870 will last you very long.