Currently have 110 outlet to a bedroom and living room.I want to change that to 120v because of entertainment center that pulls a lot of power.One receptacle will only be at used at a time, so it will be a dedicated line.I just want the other plug in wired so if I decide to move the unit.

Are you wanting to increase the amp draw for that circuit

Outlets are what voltage you have coming into your home, few are 110 but you can check voltage with a meter.

You can increase amp draw but it will require normally changing the wire and breaker.

110v and 120v are the same thing. It is all 120v.