Help: My Av Build

I've started research on the hardware and software for a build that I am thinking about executing. I couldn't find a general NAS guide, so I'm assuming this is OK.

Applications: (in order of importance)
- Important Document Storage (The wife and I are Directors of a non-profit)
- Backup Photo Storage (for my wife, she is a professional photographer)
- Movie Backup
- Music Backup
- Book Backup

Priorities: (in order of importance, I believe)
- Data Redundancy (mostly for the wife's client's photos)
- Energy Efficiency
- Data Write Time
- Data Read Time
(I think that covers everything)

I thought that a NAS would be a good solution for my situation. Just so you know, I think that I'm going to eventually build a HTPC, Gaming rig, and a photo editing monster (this might be a buy). I currently have a mediocre gaming/HTPC, and the wife has an iMac.

I was thinking raid 5 with or without a hot spare.

Hardware (?):
- Generic Case?
- 5.25in to 3.5in bay converters
- Western Digital Eco HDDs
- Raid Card
- Motherboard?
- RAM?
- Intel i3 Haswell @45w

Software (?):
- FreeNAS 64bit?

More info to come. All I can think of at the moment.