Looking to install a second cable modem. Would be that possible?

You can use a 2nd cable modem, IF, you sign up for a second line of internet service. It's like telephone numbers, if you want a 2nd telephone number, you have to pay for a 2nd line of service. 

Same with internet, you have to sign up for a second service of internet, and if you want the same speed, basically you have doubled your internet bill. 

BTW, I know what I am talking about, 16 years at Cox, about 11 of those years, in Advanced internet support Tier 2, 4 years in CAG. 

If you need to cover an office, look at a Powerline Adapter, it's 2 pieces, I have one end connected to my router via ethernet, and then plugged into a wall power outlet, and then in my office, I have the other end that has both ethernet, (Connected to a switch so I have 4 ethernet cable connections), and it also has dual band WiFi, so it's got 2.4 and 5 ghz. It's setup with the same SSID and WPA key as my regular router, so it accts as a mesh WiFi, and my mobile wireless devices automatically connect to the best signal levels.  Like my friend used to say - "Looks good, works fine, lasts long time".

The bottom line, it really does work if you get a good unit, and it saves you from having to pay for a second line of internet service.