Seeing that your present modem is connected via the USB port you will need to purchase
a combine ADSL2/2+ Modem Wireless 54Mbps Firewall Router
Sample of the type required.
Linksys Wireless-G ADSL Home Gateway Router
3Com Office Connect Wireless 54Mbps ADSL2/2+ Modem Firewall Router
D-Link Wireless G ADSL2+ Modem Router
Using the above type routers you would remove your present modem and do a total new install
Take a read at this posting on the Devolo set-up