I'm not big on those NAS boxes either. Just went around a few times on Anandtech on their latest Synology review. Not bashing it just points and something big they missed about it in the review. Anyhow;
I actually have 3 STBD4000400 (retail version) and 5 ST4000DM000 (OEM version) to build my next array. Waiting on the card. I have the system already and just need to pick my controller card and I'm done. Been using one to test initial performance as my FRAPS drive, etc. and actually it's a lot FASTER then the WD drives I've been using. It does take a bit to spin up but as long as it has a fan on it, I did a full 4TB transfer to it and it didn't heat up. Without a fan ya they get a bit warm but most cases today have fans over the HDD area making that a non-issue.
I've not been happy with these 'Reds' at all. And generally avoid Seagate by name. But something made me try these this time. Time will tell obviously but so far they are performing well. Although the DOA rates are really poor. Although much of that is NewEgg's OEM shipment methods.