Are the drops random? Or more or less consistent?
When you change drivers, do you use
DriverCleaner?
Your system is about as top notch as you can get it, so there should be zero bottlenecks that would really matter.
Modern spyware bypasses most of the SP2 security with ease, especially if you use Internet Explorer to browse the web.
Check your task manager, any strange processes running or any serious CPU load coming from anywhere?