Need help picking a router?

[john]

So I used to have a 2wire router that I used through AT&T, but now I have a faster internet connection (cable), and I am looking to buy a new router that I will mainly be using to play Call of Duty on. Anyway I don't know much about routers, I'm not sure how good the 2wire router actually was and how much I should spend on a new one. I'm looking to spend between $50-$100 at a local walmart or best buy but I'd like to know if a $50 router will do the trick or if I should spend more? Also how can you keep people from using your internet? My 2wire router had a network key. Thanks.
Internet connection is 6.12 mbps download.