Let's Make Robots!

choosing required components

I am trying to build a robot but I could not figure out how to build it since I am newbie.

My plan is buliding a robot that has 4 DC motors( 4WD ), 5 Servo motors (arm) , 10 sensors (IR and Ultrasonic) and magnetic sensor.

my main issue is finding a microcontroller board that can handle all these actuators & sensors.

In fact, I could not find any board that can control 4 DC motos (bi directional) and has output of 3A for each motor.

I know that there are a lot of shields for arduino that expands board's I/O but I do not which one to pick in order to contol  these motors and sensors.

So, could someone please explain to me how to connect all these motors and sensors to an arduino board ?