Slower than I'm paying for download speeds through wired router.

Hello. I'm hoping you can help me. I subscribe to Comcast's Blast internet package, which advertises 50Mbps download speeds and 10Mbps upload speeds. If I plug my computer directly into my Motorola SB6121 modem, I get the advertised speeds. However, through my Belkin n300 router with a wired connection, I only recieve download speeds of about 28-30Mbps. How can I best fix this? I was getting...