Power Supply Requirements

I have already bought an XFX r9 290 and an EVGA 600w psu

On Newegg it says the minimum power supply is 750w.

Along with the r9 290 I will also be running:

1 Hard Drive

Define R4 with 2 140mm fans

FX 8320 with stock cooler (won't be overclocked)

Asus optical drive

 

According to the Cooler Master PSU calculator (http://coolermaster.outervision.com/PSUEngine2)

I only need 494 watts.

Is my 600w PSU enough?

 

yes easily 600w will cover it

pcpartpicker.com has a pretty good PSU calculator but of course nothing is ever exact. You should be more than fine with 600w

Cool, that really alleviates my worries.

Thank you kindly.

the coolermaster PSU calculator actually lines up fairly well with OEM built machines (think acer and dell computers) 

which basicly means that the number they state will run, but it wont be give much headroom for upgrading, or having the PSU run at a lower usage % (think heat production and lifetime here)

I'll count on upgrading my PSU if I upgrade anything major. Which isn't a huge problem as long as I have something functional while a save money for that upgrade.

If I add like 3 fans, an ssd, some led's, and a better cpu cooler will I still be ok?

fans use very little power compared to everything else in the system and the cpu cooler is just an extra 1-2 fans depending on the cooler. you should be fine!

Coolio

Just be sure that if you have chosen one of those evga psu that have a multi rail design that you run a cable from each rail to the gpu. Apart from that you'll be fine as you're not overclocking. Fans, hdds, lights etc consume bugger all power so nothing to worry about there.