I have 2 DOCSIS2 compliant cable modems for sale. They are capable of download speeds up to 30mbps:
1 Used Motorola SB5101 modem - I changed ISP's and no longer need this modem. I was getting over 20mbps speed with this modem, includes modem, power supply, and ethernet cable. $25.
1 brand new in box RCA DCM425 modem - includes modem, power supply, ethernet cable, manual, and CD. $35.
If the modem is still in the ad, I still have it.