I have one running 5x2TB WD Green (in SPAN mode) and 2x1TB WD Green (in SPAN mode) off a E7400 + Asus P5N7A-VM, running Vista HP (32-bit) since I have a spare licence. This rig serves as my backup server. I use SPAN mode to create a large block of HD space without redundancy, as this will act as backup storage only (the main storage will be in a RAID-5 array).
I will soon be replacing the CPU/mobo with an unused Q8200 + Gigabyte EP45-UD3P since I plan on using the E7400 plus the mATX P5N7A-VM to build a NAS into my unused SG-01 casing (plan on 5x2TB HDs, 2 in the internal drive bays, 3 in a IcyDock 3-in-2 removable drive cage in the external drive bays). I have started to look around at FreeNAS to run this NAS, and the possibility of using a CF-to-IDE adapter to boot the OS off a CF card via the IDE port. This NAS would be headless and kept in my store-room next to my main home switch.
My main server should be completed by this week, as I just need to pickup a good HSF (thinking of TR's Venomous-X) and a cheap GPU (Radeon 5450 possibly) to power 2 monitors. I will be running 2x2TB WD Black (OS + fast HD for video ripping/encoding), and 8x2TB WD Green in RAID-5 off an Areca RAID controller. I know of the possible TLER issues with the Greens, but the RE4s cost twice as much, and at current prices, the additional cost is RM3.2K. So I am hoping that since I also have a full backup in my other rig and I hope I can change the timeout settings on the Areca controller, things should be ok. CPU is a i7-870 with Gigabyte GA-P55A-UD4P mobo and 8GB of Kingston VR. I've mounted 2 units of IcyDock's 5-in-3 removable HD cage in my CM Stacker casing, and plan to add a 3-in-2 cage as well for another 3 HDs. So in theory, I should have 14TB of RAID-5 storage now, with another 4TB (less what the OS takes up) of fast storage (off the WD Blacks) to speed up my rips/encodes. Potentially another 6TB of storage once I get myself down to Singapore to get my IcyDock drive cage. The OS will be Win7 HP (64-bit) at present, though I will consider using Windows Home Server v2 when it is finally launched.
I will also use my new server to test the CF-to-IDE adapter (using 2x16GB Kingston 133x CF cards) for possible use on the NAS.
Your NAS look complicating.
I m using synology NAS with 4x2TB raid 5. And a 1x2TB + 1x1TB media player network to NAS. All the storage already 70% full. I keep the rig simple. Important is using less power. My next expanding should be another 4x2TB raid 5 enclosure to joint to the NAS.