Hey guys!

I have recently ripped and ported most of my blue-ray discs and would like to move the files to a raid array, which would be connected to my Media PC.
Later on I might turn it into a Media Server for streaming, however at this time I am only interested in using the array locally and hence offline.

The Media PC runs an i3 4330, GTX 750 TI, 16GB 2400 Xtreem RAM, Samsung 840 Pro 128GB, Z87 D3H and Sounblaster X-FI with 5.1 Surround Speakers + Sub.
3x 3TB Seagate Barracudas will serve as storage.

The most beneficial raid levels with my HDD setup would be a raid 5 or raid 0 with two of them, while one serves as a backup for the most essential stuff.
In both scenarios I would lose one drive's capacity for redundancy.
Although, with raid 5 I could lose an entire drive and still be able to restore it entirely due to the parity drive, while the backup drive would only carry specific data.

Seeing as I'll need a highly expensive raid controller in order to get acceptable write speeds with raid 5, I have decided to just raid 0 two of them and use the other one + a couple of older drives for backups.
The speed benefit of raid 0 is another factor.

Now here is the problem:

I also use my Media PC for work and browsing, as I hate having to run my primary, watercooled system 24/7 for such banalities. (MCP35X needs her breaks)

Since I will primarily work/browse and only use the Media PC for movies from time to time, I don't want the HDDs running constantly, when I am not using them, as I want to preserve and prolong their life span.

What would be the best way to accomplish this?

I have looked into HDD powerswitches, separate PSUs etc., however I would imagine that rapidly cold shutting drives down on a regular basis is probably more harmful than just running them all the time.

A NAS seems like an alternative solution, where I would only plug it in when I wanted to watch movies, but I want to use some open source software, that isn't supported by conventional NAS solutions.

If you have an idea how I could use my Media PC for work and browsing, while occasionally utilizing the raid array for movies, which would only be powered on at that time and remain dormant otherwise, please post it.

As always thanks in advance.