How can I get 2 cable modems?

Im a teen who lives at home with my mom and sister

Anyways we have roadrunner and its a cable modem but my problem is that whenever i want to play online with my ps3 i gotta ask if i can take the modem in my room to play and so half the time im not aloud to

So my question is if i buy another cable modem will we be able to run the 2 at the same time

For example 1 will be in the kitchen which has its own cable line for the modem and 1 will be in my room but ill just plug my cable wire into the modem whenever i wanna play and whenever i wanna watch tv then ill plug the cable wire back into the tv .... This is kinda what i already do ... whenever im aloud to take the modem i plug my cable from my tv to the modem and it works fine

 

also if i can not do this thn ill need a good wireless router and mayB you guys know of 1 that works well but is around $100 dollars or less