As far as I know the Shield will only work on a Kepler card. I assume that means you can't run it on a GTX 580 even if you have a Kepler based card inside. I would go on ebay, sell the GTX 580, and use whatever you were going to spend on a GTX 650 to buy a 660 ti or better if you can.
You can get $180 at least out of a GTX 580 on ebay. I've even saw them sell for as much as $400 this month but that's rare and probably was bought by a confused and/or misinformed buyer. Plus with the $100 or so you would have spent on a GTX 650 you would have $280 to spend on a new graphics card. That makes this
http://www.newegg.com/Product/Product.aspx?Item=N82E16814121656 the perfect choice for you.