Well,GTX 460 can handle all games perfectly fine on your resolution,but resolutions like yours benefit from a fast CPU,so if you can afford Core i5/i7 CPUs,then go for them(you have to change your CPU,RAM and Motherboard),but if you can't,then although socket 775 CPUs are EOL,you still can find them.
A CPU like Q9650 will give you a good boost in performance
http://www.newegg.com/Product/Product.aspx?Item=N82E16819115130