Only getting 5mbs or less on download and upload

I've tested using speedtest.net as well as the cox speed test.  I have the SB6180 modem connected to a linksys WRT154G router. Lights on the modem are solid blue for send and receive. Solid green for Online and flashing for the link.  I have the same results from a PC connected to the router via LAN cable as well as a wireless touchpad and a wireless HP laptop.  I ran the tests yesterday as well as today with the same results.  I have the Preferred internet package which is supposed to have 50 MBS download speed. I am getting DSL type speeds.

Sincerely,

Brendan