Yeah it should be running much better than that regardless. I mean before my GTX 460 I was using a GT 220 and it's not a real high end card and it was running Rift at around 20-25fps on high settings, which isn't great but it's playable.
But he said it would jump to 60-62fps then just drop astonishingly. But I was running it on 1080p on my monitor and it wasn't fitting my screen. So the res probably has a lot to do with it then. He's wanting to upgrade the card anyway.
Thanks for the reply