Different Ram Sizes question

Can I put 2 2G and 2 4G sticks and make it work?

Currently I have 2x2G sticks of G.Skill ram and have ordered 2x4G sticks of the same. All the same specs, just different sizes. Can I keep my 2G sticks in and put my 4G in there too? I have enough slots, just not sure if I can mix the 2 different sizes.

This is what I currently have. http://www.newegg.com/Product/Product.aspx?Item=N82E16820231277

This is what I have purchased. http://www.newegg.com/Product/Product.aspx?Item=N82E16820231428

Thanks!

Just make sure the modules are installed in a dual-channel config. like such...

Rules to enable dual channel mode
To achieve dual channel mode, the following conditions must be met:

Matched DIMM configuration in each channel
Same density (128 MB, 256 MB, 512 MB, etc.)
Matched in both Channel A and Channel B memory channels
Populate symmetrical memory slots (Slot 0 or Slot 1)
Configurations that do not match the above conditions revert to Single Channel mode.

The following conditions do not need to be met:

Same brand
Same timing specifications
Same DDR speed
Memory channel speed is decided by the slowest DIMM module populated in the system.