You will really be a lot happier if you get an I5 in that. Even it it means you need to wait another 2 weeks to save for it, you won't regret it. Not only will you see an increase in gaming performance (especially heavy CPU titles like BF4) but your overall system will feel a lot more responsive.
I'd say the max you need is 600w bronze rated for your PSU - i think i have a 550w in mine and running a very similar setup and not had any issues.
The Toxic version of the same card (sapphire) only recommends 500w so you might actually be able to get away with it.
http://www.sapphiretech.com/presentation/product/product_index.aspx?pid=2038&lid=1#
Edit: performance wise i'm running every game i have on full graphics with a similar setup but gen 3 I5 in there. This includes archeage, skyrim, BF4, WoW & LoL. Im sure there aresome i can't but not played them yet.