To get results even worth the extra heat and noise on a 580 is the issue. I've had a Asus Matrix gtx 580 and it couldn't even handle the big factoty overclock. Even with its 3 slot behemouth air cooler 3 slots big and two turbine fans, it couldn't manage temps out of the box lower then 95 degrees (sounded like a two blow drying directly in my ears). Anyway, if you want to OC and you are gunna be happy with the factory OC of that eVGA then get it because as easy as everyone says overlocking is, there are always little anoyances that make it a pain in the ass.
Sometimes the OC program interferes with the drivers and causes alot of stuttering and low performance and you need to reinstall driver and OC program. With my last cards it happened to me almost every 2nd day. Take a look at the MSI lightning (http://www.ncix.com/products/?sku=60193&vpn=N580GTX-Lightning&manufacture=MSI%2FMicroStar)
, its 549.99 and has a better overclock and can actually handle it unlike asus. its what I have. If your gunna spend money on a factory OC card then make it a good one with better cooling otherwise get the bone stock and see if you can manage an oc that you will be comfortable dealing with, in terms of heat, noise, voltage, performance etc.
I assume you like the eVGA warranty though.