My unRAID configuration

First of all still new to unRAID. I finally got all three of my XBMC's boxes up and running.

I currently have a ReadyNAS NV+ running in x-raid (2TB X 4 Drives). Working fine but looking for more centralized data and larger capacity.

UnRaid appealed to me because it spins down the drives.

My Objective: Build the lowest power server with 8 drives. Use this server to hold all media and files, run SAB, couch potato etc... have as MySQL server.

Equipment I currently have (I know some of the equipment overkill)
8 x 3TB WD drives
1 x 64 GB SSD (Cache Drive)
1 x Gigabyte Z77MX-D3H
2 x (2X4GB) GSkill memory 1600.
1 x i5 3570K processor stock Intel Fan
1 x Silencer Mk II PS (+3.3V@25A,+5V@25A,+12V@62.4A, -12V@0.8A,+5VSB @ 6.0A)
1 x LSI 9207-8i SAS Controller
1 x NZXT Source 220 CA-SO220-01 Black Steel
2 x 120mm fans for front of case.
1 x unRAID Pro License (Pending feedback from this forum)

Here are my questions:
-- Any feedback on the build (Besides it being overkill)
-- Should I get a bigger SSD for cache drive?
-- What are some gotchas I should look out for?
-- Should I think about another RAID solution (FlexRAID, WHS etc...)

Again my goal to be power conscience.