I'll enable the auto bandwidth selection when I get home from work and see if that helps.
I have a motorola sb6121 modem plugged into the dgl5500. I have Comcast and I'm located in greenwood, in (a couple miles south of Indy).
I have a Xbox 360 wired to the router and everything else is wireless (nexus 7, 2 iPhones, playstation vita).
I have comcast's 50/10 plan and average close to 30 Mbps down and 10 up.
And firmware version is 1.01 on the router.