Second using a QNAP - we have 2x TS-869U-RP's with 10Gbit cards in and they work excellently.
The first one is in a RAID10 (as everyone wants quick storage and we don't have massive amounts of it), with 8x 6TB WD Red Pros giving ~24TB of usable storage. It's connected to our 10Gbit core, and then mapped to the file server via iSCSI (also on 10Gbit), and then shares are served through the file server.
The second one has 8x 6TB WD Reds also giving 24TB of storage, but is used for backups (done through Veeam Endpoint). Works fairly well, and very reliable!