I'm currently in the same boat your are. I have a AMD 990FX system thought so MY comment's about score's my or my not go along with yours. As the others have said "YOU NEED TO KNOW THE IC", all memory is not the same.
1st you need to read Woomack's EXCELLENT memory guide, this gives you the KNOWLEDGE that you are asking about. I can go on and on about the difference in speed from 1600 - 1866 - 2133 - 2400 memory or how much better CL8 @ xxxx speed is to CL9,CL10,CL11,Ect,Ect. IMO if you are not going to be using it for benching, save your money and pickup some DDR3-1600 CL8 memory. In a basic config that you will use for every day stuff, a increase of less than 5% for memory that's more than 12%-25% more $$$ is not going to help. You will see a better return of your $$$ by using what you saved and putting it into a better CPU or GPU.
Thank You For Your Time
In Reading My Post