Which RAM should I buy?

Solution
Are you buying a kit (2 sticks) or are you buying one to try and match it with the one already there?
Trying to match sticks can be hit and miss. Sometimes they will only run at slower speeds and other times they drop down to single channel mode.
Your two options are: buy the EXACT same mfg. model that you currently have and try it (good luck), or, buy a 2x4GB kit and replace what's there. If you just want to buy one stick, try to match whats there exactly. If you can't find a match for what you currently have it would be best to just buy a kit (2x4GB). If you do this you could get a 1067 or 1333 kit - if you get a 1333 kit and your system can run at 1333, it will.
Are you buying a kit (2 sticks) or are you buying one to try and match it with the one already there?
Trying to match sticks can be hit and miss. Sometimes they will only run at slower speeds and other times they drop down to single channel mode.
Your two options are: buy the EXACT same mfg. model that you currently have and try it (good luck), or, buy a 2x4GB kit and replace what's there. If you just want to buy one stick, try to match whats there exactly. If you can't find a match for what you currently have it would be best to just buy a kit (2x4GB). If you do this you could get a 1067 or 1333 kit - if you get a 1333 kit and your system can run at 1333, it will.
 
Solution