Recommend you get the following:
PSU: LEPA G1600 - 1600 Watt power supply
GPU: MSI R9 280X <- You can overclock easier with MSI afterburner.
Now, regarding the build itself:
I'm planning to work with R9 280x cards. I'll start off with 2 cards, and eventually build it up to 6 cards in the rig. Regarding this, I have a few questions:
Someone suggested that I split this between 2 rigs, so as to not keep all my eggs in one basket. I definitely understand the wisdom in this; however, knowing the fact that a computer alone will cost me as much as roughly 1.5 GPUs or 2 PSUs, would you suggest that I go for two rigs or one?
I recommend get a most powerful PSU, then you can run 6 GPUs in one rig. LEPA G1600 can power 6 GPUs.
How much power will I need to run 6 cards eventually? The highest available PSU in the market is 1200W. I don't think this will be enough. So eventually, I'm going to have to add a secondary PSU anyways. Keeping this in mind, what should be the rating of my PSUs? 2x 860W or 2x 1000W or 2x 1200W ? Note that I will try to under-volt the cards, but I don't want to rely on this.
Is Corsair better or Seasonic better for PSUs ?
Does the Platinum/Gold make that much of a difference? I'm less concerned about the power draw off the wall, and more concerned about the safety of my hardware.
You can run 6 using LEPA G1600. Platinum Rating is better than Gold.
I was planning to use ASRock 970 Extreme 4 as the MoBo, but I read on a thread that it only supports up to 5 GPUs. Which MoBo can I use for 6 cards if I decide to go for the one rig option?
Related to this question, the ASRock 970 Extreme 4 is an older board, if I'm not mistaken, and its availability is dicey. Which MoBo is everyone using these days for their rigs?
Get this mobo --> MSI Z77A-GD65 Motherboard (Intel Core i3/i5/i7/Pentium/Celeron, Intel Z77, ATX, RAID, Gigabit LAN, Socket LGA1155)
You can have up to 7 GPUs using this one. This is the one I am using.
You will need Intel Celeron, i3, i5 or i7. I am using i7, because I am also mining CPU crypto such as Quark, Primecoin and Protoshare.