Misconfigured Router: Slow Internet Data Transfer

[eldiablopotato]

I can't quite figure this one out...

Testing my Comcast ISP download speed via speedtest.net it's 13MB (when the computer is connected directly to the router). When I put my new router (fully updated firmware) between my cable modem and computer my download speed is now 6MB!? I understand that I'd take a little performance hit, going through a router. Would you guys agree that something odd is going on?

The router I'm using is:
D-LINK Xtreme N Gaming Router (DGL-4500)

 

[spidey07]

Make sure you don't have a duplex mismatch on any port on the router. Leave all ports and all network cards set to autonegotiate speed and duplex.