You would definitely see a MASSIVE improvement in games with an extra 2gb of ram + a new gpu. Your cpu is still pretty ok by todays standards.
Now it depends on what your preference in graphics are, if you want to play most games on say medium/high settings at 1920 x 1080 then I would just grab a 7750 and call it a day. If replacing your psu is fine, grab a 650-750w and a 7870http://www.newegg.com/Product/Product.aspx?Item=N82E16814150605
Either way atleast some gpu and atleast another 2gb of ram (id go with 8gb since its only around 40 bucks right now) would be a massive improvement.
And Ivy bridge onboard gpu isn't really all that good for gaming