billaustinthey call me Mr. BillPremium,MVM
North Las Vegas, NV
Theoretically, the modem should not matter if it is a current model and your line stats are good. The router is more likely to have an impact on function, especially if there are a lot of active users. If you are expecting heavy use, or a lot of active connections, I would recommend bridging the modem and getting a separate router of good quality.
All current models supplied by CL are modem/router combo units. If you need a new modem, I would recommend the ActionTec C1000A. It is a modem/router combo and works with both ADSL and VDSL circuits. You can get it at Best Buy for $99 in CenturyLink packaging, or you can rent it from CL for $5/month.