Can I add a second Cable Modem ?

I currently have a CM400 Cable modem & Netgear Wifi Router connected to my cable connection in my living room. Works GREAT! My Xfinity service is connected and the equipment is activated. My phone service is Vonage VoIP. The house has a seperate office and my wifi reaches that area just fine, however, my new HP Printer/Fax machine doesn't ike the VoIP for sending or receiving faxes over the phone wiring. HP recommended that I change a few fax settings and connect the phone line directly to a Vonage box. Not to use the wiring in the walls. I'm thinking that if I connect another CM400 to the live cable connection in the office and then connect another Vonage box right next to the fax machine then the fax might work. Can I have two cable modems connected to the same Cable system?