My question is "Why do you want or need 6GB of RAM?"
It will work as they match in voltage, timings & MHz. However, there are very few appilications that will benefit from more than 4GB of RAM. In those cases, you be better off with getting two sets of the 4GB kit, so you would have 8GB of RAM
Yes they are compatible. They are the same memory standard, no matter the different models or brand. Don't listen to the guys who say, why do you want or need that much memory.. they are the broke ones who could not afford it, which is why they are trying to get you to buy less. Trust me you will need 6gb sooner or later and it is best to have it now so that you do not find yourself having to order again.