When you order cable, they usually will charge for a modem anyways, and you just have to give it back when you end your contract with them. It may be cheaper to just buy one.. I'm not real sure. If you need a router though, go D-Link or Linksys.
ive already got a router, its a d-link. the cable company wants to charge $10, and i believe that is a monthly charge??? and with this modem, its $100, but there are $90 in rebates, so i would just assume pay 10 dollars and get my own, then pay 10 and have to give it back