Wow, your current one definitely needs an upgrade. Most of your components run on the 12V rail, and your PSU only has 156W available to things running on the 12V rail.
I would suggest something more powerful than the 7600GS, maybe something like a 9600GT or a 4670 or a 5670, either of them would be significantly more powerful and wouldnt need a strong PSU. A good cheap one is the corsair 400CX, it will easily power a lower power card.http://www.newegg.com/Product/Product.aspx?Item=N82E16817139008
It may not seem all that cheap but realize that the super cheap PSUs have explosive tenancies and tend to take out other components when they go.