Here's what I recommend as a starting point for a good edit system.
F: Global Cache (Optional, for heavy AE users)
H: Images (Optional, used if you deliver DVD or BD)
Fill in the primary five slots before you start making RAID arrays. Plus some type of backup/archive solution.
The suggestion to use identical disks is solely based on the flexibility to create Raid arrays somewhere in the future. You can only create good arrays if you have identical disks. If they are different you either have a JBOD (just a bunch of disks) or you throw away the space difference between your smallest disk and the others in the array as unusable. Say you have one disk of 320 GB and a number of 2 TB disks. If you create an array, all the 2 TB disks will only be used as if they were 320 GB disks. The rest of the space can not be used.
Your motherboard can easily accept a dedicated raid controller, but do you need one? They don't come cheap and it depends on things like source material, complexity of your projects, workflow and your own patience. There is no straightforward answer to that question. To give you some more background on raids, have a look at To Raid or not to Raid, that is the question.
Your green disk is only usable for backups. Jim's suggestion is a good one as a starting point, but if you encounter jerkiness, choppy playback or consider the editing experience as less than fluid and is taxing your patience, then a raid controller can be a nice but somewhat expensive addition. Before you decide to go that route, I would first suggest you up your memory to 32 GB.
Thank you Jim and Harm,
The memory I had was Corsair 16G(4x4GB) Vengeance (CMZ16GX3M4X1866C9 1866MHz DDR3 CL9) and I added that same memory again to the remaining four spaces on the motherboard (ASUS p9X79 deluxe).
The motherboard specs say it can handle it but the processor specs say the # of memory channels is four.
So, should I and can I get rid of the current memory and get 4x8gb so it will fit in the four memory channels or would it be easier going for a new processor that accommodates eight channels and use the memory I already have?
I have 2x1TB caviar black disks already. If I'm going to add more disks so each one has a dedicated purpose (like Jim's suggestion) can I just get the rest Caviar black 500gb? If the 1TB disks will act as 500gb disks once in an array, this won't be a problem if 500gb is enough (despite the space loss).