Look, i don't know if the 500W model you indicated on top (500 watts hunt key) is any good, it's not even see it in the Tom's hardware forum list of PSUs (http://www.tomshardware.co.uk/forum/id-2547993/psu-tier-list.html),
so considering the good (and expensive) hardware you're buying, you should definitely buy a good PSU. However, i don't think you need more than 500W (say 600W if that makes you feel better
), 1000W is throwing the money, 850W is way overkill. Check the PSU list to select a good one, but don't pick the one with more wattage, that won't make it better.