I just went though this a few weeks ago as I built a system very similar to yours (see my signature) and did a lot of research. Most of the wattage calculators you find here and on other sites will rate your parts a lot higher then what is required. As an example mine was rated at 450 watts but in total going by how many watts each part used it was about 285 watts at idle.
Of course you want to factor in load and overhead but don't be afraid of stepping down to a lower wattage then that Ultra x3 1000Watt your using now. It's the quality of the power being supplied vs the total wattage so big is not always better. I stepped down from a Rosewill 850 watt to an Evga 650 watt and it's a more powerful unit. My total under load is about 389 watts so in theory a 450-500watt quality PSU would do but I went to 650watt for maximum overhead.
While asking in forums is helpful I found the best advice from the guys that break these units down to see what they are made from. One site I always use is
http://www.jonnyguru.com/ and I always base my purchase on the evaluation and review of the unit being tested. So far in the last 10 years they have not let me down and the PSU I just purchase
"Evga 650watt G2" was a 9.6 out of 10 and recommended. While sites like Newegg and Amazon can give you a general feeling for it in the reviews section it's hard to match the guy ripping it apart to see what it's made of.
Anyway from the Specs you posted I would not hesitate to recommend the unit I bought but I would tend to stick to the G2 units of EVGA as some of the others have had issues and I would make sure that whatever unit in your price range was reviewed and had a high rating on Jonnyguru's site as they have never steered me wrong yet. If your not intending to do crossfire/SLI I think anything above 850 watt is overkill. As Bob16314 posted above their is a "Tier" list that's useful but don't be bound by it as there are some very nice unit's in the second Tier and quite a few other manufactures.
You'll need to find your sweet spot of Price-Quality-Wattage-Warranty to make a solid choice but above all else do the research so you don't end up with a power headache down the road if things start going south in a few months/years.
If you need more assistance then just post the link's to what your looking at in this thread and we will try to help you out.
Good Luck!