Hi guys , I know u r going to advice me to use the PSU calc. but I need to get an advice from u , cos u guys have more and good exp. I am building a new sys. and am planning to by the Ultra 4X 750W (PSU) , so i dont know if its enough for my new system or not , my new system is: Asus Rampage III extreme , i7 980X , ocz (vertex 2) 90g and (vertex 2) 120gb , 1 velociraptor 600g 10000rpm 32 mb cache sata 6.0gb , cooler master sniper black case , ram 12gb ddr3 PC 15000 , ultra chilltec thermal elec cooler , dvd burner , PNY gtx470 , plz any advice it would be appreciated and thnx inadvance.
OP: If money is important to you at all, you are spending it in all the wrong places. Since you aren't a gamer and don't plan on OCing (if you're not heavily into games and/or benchmarking, you really don't need to be OCing as all that will do is crank up your power bill), the Rampage III board, the velociraptor, the pc15000 ram, and the cooler are a HUGE waste of money.
1) For the Rampage III, you are basically paying a hefty premium for a board that can overclock well. Since overclocking really won't help you much (especially with a 980x), you can easily get away with a board that costs a lot less.
2) You already have a couple of SSDs for speed. The velociraptor is not worth it in this case. Its only advantage (much faster boot up) will be taken care of by your SSDs. I can tell you that I went from my last gen velociraptor (300gb) to a Samsung F3 1TB. Speed actually felt faster with the latter. What's more, the Sammy is much larger and only cost me $58.
3) For ram, the cheapest DDR3 that runs at 1.5v will be indistinguishable to you performance-wise compared to the fastest clocked DDR3.
4) Like many have said, the stock cooler is good.
With parts this expensive, like the 980x, the LAST place you want to skimp is the PSU because if that blows, it can take your expensive system with it. Don't skimp on the PSU and don't skimp on the case. A good case ensures you have excellent airflow whereas a bad case is just asking for trouble even if you have an expensive cooling system.
And to answer your question: A quality 650watt unit will actually reliably output MORE power than a crappy 750watt unit. Case in point: There was a crappy Diablotek 1050watt psu reviewed that literally blew up when the reviewer tried to put a 50% load on it (it couldn't handle the 525 or so watts, let alone the full rated capacity.)
The system in my sig at PEAK draws like 250watts (40 of that is my monitor, so only 210 at peak.) Yours draws more than mine but not more than 300 watts or so. Don't be fooled into needing more than a 600 watt unit if that.