Upgrading To A Real Whs

Hi, new here and fairly new to whs. I've converted an old amd 3700 running whs2011 and it has 3GB ram installed (2GB usable). I have an 80GB PATA OS drive and 4 1TB drives in software raid 5 coming out to 2.72TB of usable storage. I'm currently in the process of converting my blurays to mp4 when i noticed one of my hdd is going (the sata connector for power and data are broken). I wanted a real server anyways so this give me an excuse to build one. So here goes.

Case
Fractal Design Define XL
Processor
Intel Core i3-3220
Motherboard
SUPERMICRO MBD-X9SCL-O
Memory
Kingston 16GB (2 x 8GB) 240-Pin DDR3 SDRAM DDR3 1333 ECC Unbuffered Server Memory Model KVR1333D3E9SK2/16G
HDD
some boot drive
3x WD20EARX or Western Digital WD20EFRX Raid 5 for movies, music i have an EARX sitting around so i could just buy 2. Performance difference?
4xHitachi Deskstar 1TB Raid 10 for family photos and important files (taking from existing server and replacing the broken hdd)
RAID controller
HighPoint RocketRAID 2720SGL
Power Supply
SeaSonic SS-660XP 660W ATX12V / EPS12V 80 PLUS PLATINUM

First time building a server, I've been building my personal gaming computers since 2000. Any help would be appreciated. Looking to consume as little power as possible while still meeting my needs. I stream using Plex. Thank you for your help guys.