Without a doubt I'd go for a GTX 460 on ebay and overclock it to 850MHz and 2000MHz memory. At that speed it outperforms a stock GTX 560(non-ti). And then (if your motherboard and PSU supports it) you can buy another GTX 460 and SLI them. For $200 you can get performance greater than that of a GTX 580.
Those passmark scores are not accurate. The CPU charts are a little accurate but not the GPU scores. I have a whole lot of trouble believing that the GTX 570 is better than a GTX 690. It just simply doesn't add up. Don't get me wrong... The GTX 570 is an excellent card but it just plain sucks against the GTX 690.