Hi. I'm a computer technician:
First of all, most motherboards support DUAL RAM. Some boards (x58?) support TRIPLE-Channel meaning you'd install three sticks at a time.
Unless you are editing video (not just converting it) and require large amounts of RAM the absolute MOST you would need is 8GB.
If you have a triple-channel setup get 6GB (3x2GB). If you have a dual-channel setup get 4GB or 8GB. You'll see little advantage with 8GB.
How does RAM work?
When your computer first starts, windows and all your programs are on the hard drive. Parts of Windows and other programs are copied into the System RAM because it is much faster. Basically the CPU is like a guy reading an instruction book, and the RAM is the book.
For example:
When you first start a game, chances are it's ALL on your hard drive. You will wait while it copies MOST of the game into the RAM which might be as high as 1.8GBytes. Now the CPU is reading the game instructions out of that RAM and executing the instructions (including sending data to the graphics card to process).
Summary:
- get 4GB or 8GB of RAM for dual channel (DDR3 likely. 1600MHz is optimal price)
- 6GB for triple-channel (again, see motherboard manual)
- run MEMTEST to make sure your RAM is stable
- if you overclock your CPU, make sure your RAM is still running at the proper speed (such as 1600MHz) and not overclocked. You may have to adjust your multipler in the BIOS. Rerun Memtest if you change the CPU or RAM settings.
- update your BIOS if not up to date.