I don't think it is possible to have to much power? That doesn't sound right.
Did you try reseeding everything? Meaning take everything back out and redo it.
If not i would do that first and make sure everything is pluged in tightly and were it should be. Make sure to de static tise your hands. Common knowledge = P ( you know this already about the static )
If that still doesn't work try putting in your old psu and graphics card and see if it turns on. If it does, then there's a problem with something.
If it does turn on with your old hardware, try putting in the 850Power supply then see if it starts up. if so try the card, if it doesn't work with the card theres your answer. could be just a bad card?