How would this be? I have 550w PSU sitting in the box completely unused in my other room to replace the 300w that comes with it. would i need to buy a GPU for this? http://www.newegg.com/Product/Product.aspx?Item=N82E16883227446
Yes you would need a gpu.
You could go with something like thishttp://www.newegg.com/Product/Product.aspx?Item=N82E16814130744
My friend has the 550 ti and gets 60+ fps on ultra in populated cities.... Only downfall is it is refurbished
so it's up to you. Would put you over your budget by about 18 dollars.