Chances are, if you're getting lag with a system like that. You're not running OpenCL on your cpu. i-7's are absolute monsters when it comes to doing the Gravity calculations. But, Intel doesn't include the drivers by default. You need to download them manually, or use the generic drivers from AMD.
If you need any help with that, just let me know.
As well, If you send in a performance log with Atten : C7, why does it lag? As the contents of the feedback message, I should be able to tell you exactly what's going on. (Instead of guessing, as I am right now)