How do i bring out my Internets true potential, i am paying for 20megs from qwest, now centurylink, i get it through the phone jack into the modem, the modem is a ZyXEL PK5000Z. i can never download anything faster then 2 mbps ever, Speedtest.net says im get just over 15mbps but its wrong somehow, obviously there got to be something im doing wrong...