I wouldn't consider the Crucial its to slow. I have no information on the Kingston. For your RAM, you could pull the accessible 4gb and put 2x 8 or 16GB, insure you match the Voltages and Timing of the 2 sticks you can't get to they have to match.
Nearly all user here are using Samsung 951 is what comes stock, some are add on or replacing with 950 Retail version. not saying they wont work just we don't have many users here to evaluate. Someone that may have tried them should pop up and give you an evaluation.