I found this on the rift forum, thought it was a nice (none benchmark) way of locating your bottleneck, if the game runs badly:
You can tell which part is holding you back, your Video Card or your CPU/Motherboard by running the test below.
Put all your settings on LOW and check your FPS.
Put all your settings on MAX and check your FPS.
If your FPS on Low is BETTER then your FPS on Max, Then you need to Upgrade your Video Card.
If your FPS on Low is ABOUT THE SAME as your FPS on Max, Then your Cpu/Motherboard is bottlenecked and you need better.
http://forums.riftgame.com/showthread.php?63241-What-should-I-get-to-improve-my-FPS