I want to replace my router - it's several years old, and I keep having to replug it in every time I want to use my laptop in order to get a signal. Also, I currently have a comcast modem, which works fine. I'm just confused about which one to get. There is apple express, apple extreme, and apple time capsule. Which one is the best? I would like the back-up capabilities of time capsule, but is this also a modem AND a router? I only need a router, not a modem. Sorry if these are dumb questions!