Not sure I understand the question as posed. So let me answer some others and add more questions
I use a ton of tabs in Chrome so it pretty much uses up all of the ram.
I currently have Win8 64bit. Its showing 3.5/4 gb being used. All I have open is Chrome, Windows expolor, some hardware monitoring CPUID, and foxit pdf.
All of the ram will be the same, 1066mhz 5-5-5-15. Its not running at that atm cuz my mobo auto set it to 667 5-6-6-15, but I'll change that shortly.
I don't quite understand the channel system so that's why i wast sure if it made sense putting in the additional sticks of a different size.