Lost finding an upgrade to my Geforce GTX260. Can anyone assist?

I am looking to upgrade my video card for 100$ or less but I haven't looked at graphics cards for a while and am feeling a little overwhelmed trying to find one. The card will be strictly for gaming, specifically for Guild Wars 2. Looking for specific suggestions or possibly a link to a good guide on what to look for in a gaming graphics card. I greatly appreciate all assistance anyone can provide.