According to Newegg.com's power supply tool and your provided specs, you'll probably want a 400W supply or better. If you don't want to spend a lot of money, but still want the game to look decent, I would buy this:
http://www.newegg.com/Product/Produc...82E16814161334
You really want to make sure there's room for it though. If it can't get good air circulation it won't run as well. For power supplies there are a ton of 450W that cost less than $50. Just be sure to read the reviews before you order.