What processor could I use?

Sorry for the Re-post, but I had to edit a few things and for whatever reason I wasn't able to change any of the text.

Hello AskReddit,

I'm having a bit of a problem right now. I have this computer and over time I upgraded many things such as I added 2 more Gigabytes, upgraded to the Nvidia GTX 260, and a added a 700 Watt power supply. I have this motherboard. What I need now is a new processor for me to be able to play now a day games. My question is what processor would I be able to get that would be able to get that would be good enough to run such games as Battlefield 3 (I know not ultra, but just medium or even have a high fps on low)? My spending limit is about $250. Thank you so much for your time and any response.

Respectfully, Brimblood

This is my computer: http://support.gateway.com/s/PC/R/1009488/1009488sp2.shtml

This is my motherboard: http://www.laptopteks.com/Gateway/Desktop/Gateway-Home-Computer-GT-Series-GT5453E-1009488/Motherboard-%28System-Board%29.asp