|"If I leave my CPU at 3.6ghz will I notice a gain in performance using DDR2 1200 ram over my DDR2 800 ram?"|
In a word, no. With a Core 2 system, you'll get optimal performance with the CPU & RAM running at the same base frequency.
1600MHz runs at 400MHz frequency,
DDR800 runs at 400MHz frequency.
Assuming that is how you have your system setup, it's already optimal. No changes are necessary.
I'm curious what you use your system for that would require 8GB of RAM?