memory for asus N550JK

I just got my new Asus NJ550 laptop.Did not realize the 8GB ram was one DIMM . I am only running 64 bit single channel because of this. The ram listed under Crucials scanner is 1.35 v DDR3 12800. I believe it to be DDR3L . Can I add 1 Single Dimm of 8GB of another brand.in the second slot. How critical is matched pairs? It has Samsung in the first slot. Sandra does not specify if it is standard or low voltage. Also does anybody know if removing the back panel would screw my warranty?

Warranty - You have to read the fine print. In some cases, the RAM and HDD are considered user replaceable items (which requires you to remove the back panel) and sometimes they aren't.

When you pull off the back cover, look at the sticker on the RAM. I would think that any 1.35V DDR3L memory would work fine (if that is what is in there). I've mixed and matched memory in laptops before and they detected dual channel without issue.

Well if it's running at 1.35v that is low voltage DDR3 also known as DDR3L. You should be able to fit any 8GB DIMM as long as it's running the same timings and voltage as your current memory.