I got a new modem that supports up to 300Mbps, and when I plug my Mac mini directly into the modem, I get speeds of up to 350Mbps. However, when I put my router (Netgear wndr4500), which has 10/100/1000 ports for LAN and WAN, in between them, I am only getting about 100Mbps. I am running DD-WRT on the router as well, but I tried it with the stock router software and the same result occurred.
Note: I tried using different cables as well, all of the Cat5e variety in case that was the issue, with no effect.
Note 2: When I open up the Network Utility on OS X, it says the link speed is 1Gbit/s.