PassMark's site is good as well.

http://www.videocardbenchmark.net/high_end_gpus.html

They also have charts for CPUs as well. You do have to be careful reading them though. The GPU charts, you'll see on high end, 680 is above 690. The 690 is actually two chips in one, so with SLI on it should outperform the 680. Depends on the game and drivers, etc.

On the CPU side, they seem to use a bench that actually uses all cores. So a 6 core could be higher than a given quad core, but because the quad is faster per core, it would perform better in games.

So, grain of salt stuff.