I suggest waiting for a 1070. The 970 was awesome when it first came out and is still a very nice GPU, but it doesn't make sense to buy a new one.
HP 1U PSUs go for about $15 for a 750W unit, far more than what any GPU will ever use. (Or get a 1200W unit for $20 and have loads of power to run a nice subwoofer amplifier!) Some new GPUs don't use the 3.3V rail. If the 3.3V pins on your GPU don't go anywhere, you don't need to supply them. Otherwise, a small buck converter will do the trick.