I would get CT2KIT51264BA1339 x 2
The top two things RAM related that I suggest paying attention to are the DOA rate as in having a broken stick (or more than one) and having to do configuration before it will work.
Both those are absolutely limited with the above suggestion almost regardless of what setup you have. If your board can reach 16GBs, it can pretty much reach it that way just fine.
ECC means error checking as in the RAM checks itself before doing things, which makes it much slower. It is only ever used for server systems. Non-ECC is good enough for everything else.