lookin for new radio equipment
Snow,
Is this a car or truck? It sounds like you are talking about servos. Those are the things that are connected to the RX (receiver) that steer, make the throttle move, etc. There are many choices for you. Each servo has a designation on how much torque and speed it has and whether or not it can run on 4.8v and 6v.
If this is a car or truck, you might also want to post your question in the car section. I'm sure someone has done the upgrade you are talking about.