I looked up your motherboard and it is supposed to support 1066/1333/1600/2000 DDR3. With the new i7 architecture, I'm not sure the RAM is supposed to be bottlenecked as much as it was by the Core 2 architecture. This may just be a setting you have to change on the BIOS. Have a peek around, and see if there's anything you can change regarding memory frequency. Be very careful though, you don't want to change a QPI and end up overclocking your processor.
As I am typing this post, I just realized that while your motherboard supports a QPI of 6.4GT/s, your processor only performs up to 4.8GT/s. This may be the reason behind your bottleneck.