Well, I wanted to do a final follow up to my thread.
As it turns out the annoying buzz I was hearing with my build was the fan motor on the Silverstone power supply. After reading more reviews, it seems that many have this problem, and also many suffer PSU failures after a few months. So, those factors, in addition to the Silvestone DS380B case lacking the cooling needed to keep my drives cool. I decided to get a new case and power supply. The Case is a Lian Li PC-Q26B and the power supply is : EVGA 220-G2-0550-Y1 80 PLUS GOLD 550W . So far I'm pretty happy. The power supply is completely silent now, even with ECO mode turned off (fan always spinning). The case is also quiet, I did have an annoying rattle, turns out it was the slider to lock the hard drives in place. If I put it all the way in the locked position, it rattles, if I lift it just a bit, it's fine.
My Hard Drives now operate at 36C and while copying lots of files for extended periods of time (hours) one or maybe 2 in the middle will reach 40C.
Overall, I really like this case, but there are a few things that I think could be better.
1) I'm not a fan of the snap-in panels.
2) to remove / clean the dust filters on the intakes, you have to remove both side panels. (by contrast my PC case, Antec P182 has a little flap you open for each filter, for easy cleanup.
3) I find the front inlets are small. As you can see from the pictures they are on each side of the case, but are very narrow, the front part of the case is solid aluminum.
4) no filter for the power supply air intake at the bottom of the case. (Plus even if there was one, good luck getting to it)
About the PSU, so far I love everything about it, nice long cables, 9 Sata power connections, super quiet even with fan always running. The only complaint I had with it, is the MB power cable, where all the many wires start forming a circle (from their flat layout at the connector) is too thick and very hard so It didn't fit properly to route it behind the motherboard and up through the designated power connector cutout.
I lost the hot swap ability from the SilverStone DS380 case. Also one nice feature with that case, is that each HDD had it's own 'activity' light. The Lian Li does come with 1 hot swap backplane that can handle 2 drives. But I decided to remove it and just directly connect each drive. Plus the DS380 provided some nice capacitors to offset the power draw when a disk spools off, the lian li didn't have that.
I also have Plex setup. I tried to update to FreeNAS 9.10, (all I had setup at that point were 2 CIFS shares...) but it failed, got some error when entering the guid. At this time, I'm too dumb to properly trouble shoot it, but I have plex going now, I started copying my data from my computers to the NAS box, so at this point I'm happy with 9.3. I'm hoping to become more familiar with it and take the plunge with 10.x whenever that becomes a stable release.
Thanks again to everyone that helped me on the forum so far!