So I currently have 4GB RAM (Crucial ballistix sport, 1 chip of 4GB) and wanted to upgrade it to an 8GB RAM, with another chip of 4GB. But where I want to buy it, they do not have any 4GB Crucial's anymore, so I was wondering if I could add a Kingston Hyper FuryX 4GB to it, so that I have 8 GB in total, but from 2 different brands. Both are ofcourse DDR3-1600.
It will be fine as you have already stated that they are both DDR3-1600 and both 4GB. Make sure you don't put a stick that is above or under 4GB in there though, and read your MOBO manual to see which channels to use for 2 sticks.