You have the specs close to the recommended list for the game. That being a gtx 560 and 4gb of RAM and a quad core CPU. So by gaming standards it would be playable at medium to maybe high settings.
However, if you want that ultra preset your CPU GPU and Mobo must be upgraded. I would recommend a gtx 960 (200$+free Witcher 3), an fx 6300(minimum) or intel i5 of some sort (like 4670k), and a corresponding Mobo with the matching socket.
It is an expensive upgrade but if you really want the max settings thats what you need.