I was reading up on storage systems used in other production houses but it's either Drobo or an unnamed NAS... still looking for the best advice here.
Single Thunderbolt drives are fine as work drives if the media is standard HD codecs such as Pro Res or DNxHD. The Qnap network storage are fine archive devices. We normally recommend Thecus because their management software is good and the build quality for the storage unit is solid. However I have also dealt with QNAP and they are solid as well. Qnap is normally more expensive.
Second the choice of QNAP and Thecus. Both are reputable brands. I use Thecus.
I've pitched the solutions between the QNAP and a smaller, cheaper Synology.