1)Why WD purple? Wasn't it for Surveillance ?
2)Wasn't the SSD pro better? He use it for OS only
3)Any reason why use this GPU?
4) 850w is enough for Sli?
1. Doesnt mean its for surveillance you cant use it for your own PC. It spots about the same speed as Black. But you must understand that you wont need a WD Black as you already have an SSD. Adding WD Black is just adding cost blindly as most of the things in the HDD are either movies or some pics.
2. Pro is better of cause no doubt about it. But can your eyes see the split seconds difference? SSDs are generally very fast. The difference between the EVO and the PRO does not justify the price/performance ratio. Pay more for that split sec.
3. MSI has a very thin profile card cooler. And among all the brands, MSI have emerged to be one of the coolest card out there to offer. You can pay a bit more for the GTX970 Gaming edition. Its even thinner and even cooler. Its good for SLI profiles as it offers just 1.5 slots worth. And the temps you will love it.
The Armor edition is something different. It spots the same PCB as Gaming edition. Just a lower end cooler is implemented. Search around Twin Frozr Club, Clon22 have given some benchmark results and also temp overall results for the both of it. See what you really want.
4. Same repeated question asked. Yes its in fact over powered. You are powering 2 polar bear friendly cards and does not even take up more than 200w per card. You still have half the maximum wattage to play with overclocking.