PSU efficiency for a 5820K build with R9 390

PleaseHelpMeTYVM

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Oct 18, 2015
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Light 1080p/1440p video editing + streaming games on Twitch: 5820K, Asus mobo, D14, 16GB (or 32GB) of RAM, SSD, HDD. 2-3 monitors. Single GPU (don't plan to CF or SLI). No OC (at least for now).

Future plans: adding 2-3 more HDDs and another SSD, maybe even a sound card as well as replacing the R9 390 for a better one and more RAM.

How much wattage should I choose so I can have a more efficient power usage and a quieter PC? 650W? 750W? 850W? Platinum? Gold?

I am aiming for a EVGA SuperNOVA G2 or P2 power supply but I don't mind going with a different brand that offers a more silent PSU.

Thanks.
 
Solution
You said you did not plan on running crossfire or SLI. I don't see any reason to get a psu bigger than 650w. 650w already provides plenty of overhead.