I will recollect that the DR 680 only accepted cards to 32 GB. I never had an issue with a single card, but I used only class 10. I used Wintec mostly, purchased on Amazon, but also EMtec which was the microcenter cheapie.
For the DR680MKII which I now use, I can go to SDHC cards, so I use a Sony (Class 10) 128 gb and 64 GB and rotate 4 cards all purchased through B and H.