I've located the Mushkin Blackline that I used for my 3x2GB setup. Lately, I've been hard on the tabs and RAM and I'm constantly at 80% memory usage. I'm thinking of filling up the last 3 slots in my setup with a 3x4GB of the same RAM.
Is this going to work? Or do I need the same 3x2GB for a total of 6x2GB sticks?
Yes it will work if you install the modules in slots of the same color. Then they will run as the second set of triple channel memory and can be of different size than modules in first set (other color slots). Make sure to buy modules capable of same clock speed and timings.