Not sure if this is relevant anymore, being September and all...
I have built over 20 of the DN2820FYKH Nuc's over the past year, and came to the conclusion that they are pretty finicky when it comes to memory. Started using the low voltage 1.35V Mac memory from Corsair and even then had a couple that just wouldn't post/boot.
I was fortunate enough to have one for testing purposes, so it made my troubleshooting a little easier... The speed was not much of an issue for me, it would clock down if I went with the 1600, based on availability.