I have Xfinity internet at 15mbps. I just upgraded the modem to the Motorola SB6141, but I want to make sure the router I'm connecting also supports fast internet speeds. The router is a DLINK DIR-628. I have to get at least 8mbps, but obviously want to get as close to the 15mbps I'm paying for. Can someone tell me if I need to upgrade the router as well?