Good video card upgrade to play TW: Shogun 2 on Gateway SX2803-25e

[Chimaera100]

I recent bought Total War: Shogun 2 and once I ran it on my computer I figured I needed a graphics card upgrade because I could only run the game decently in low settings. I have a Gateway SX2803-25e Intel Pentium Dual-Core processor with 6GB of DDR3 RAM, a 1TB hard drive and integrated Intel X4500HD graphics. The power supply is 220w. My price range is around $100 and I also plan to add 4GB of RAM. what would be a good graphics card around my budget and without having to upgrade my PSU?

 

[suteck]

^ + 1 HERE'S A LINK to newegg with a handful of the 6670's