650 watts is the minimum for a reference design R9 290, interestingly for both X and non-X models. You should be good.
http://www.realhardtechx.com/index_archivos/Page362.htm
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update:
ouch a 8320, you need to overclock the crap out of it, to minimize the bottleneck, problem is those CPU's are terribly inefficient and weak. An overclocked FX can use over 200 watts itself
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