You already have a high-end GTX 5xx series card. In my opinion you have two options:
1) Sell your GTX 570 and put that money towards an GTX 770 (when released). IMO, anything less is a waste of money.
2) Keep the GTX 570 as a spare For when the high-end GTX 8xx series cards are out and go with a GTX 870/880.