I didn't bother waiting for an answer because it's probably obvious. I ordered a 3rd PCIe cable from the CableMod store on Amazon. The product description states it's for the Corsair RMx units. A few threads on google pointed me there. I'm sure it will be fine. Turns out the 1000w version of the RMx comes with 3 PCIe cables by default. Yes, I'd rather pay a few extra bucks initially to have it come with the 850 PSU by default since GPU's like ours need that 3rd cable yet can make use of the less than 1000w boxes. In the meantime until it's delivered, I read to use the daisy chain in position 2 & 3 to make due, although not optimal, because slot 3 uses less power. Lot's of people do say it's fine to daisy chain permanently btw. I'm just choosing to not go the route since the stuff is expensive to risk damage.
I also ordered a GPU sag pole since this card is much wider than my old card. I had a UpHere bracket to help the weight distribution on the old card, but but now this bracket extends across the fan area too close now.