Let's Make Robots!

Startbot

Need assistance with potential Arduino bot.

First off I apologize if I broke a rule by putting assistance in the title. Now about my problem: I am putting together a parts list for a Arduino version of the Start Here robot. I am not sure if I need a motor controller shield for the Arduino board. I am going to use 2 4.5v DC motors and a ultrasonic rangefinder sensor(5V according to yourduino.com) and I don't know if the Arduino Uno board can handle the power requirements. I was going to use a 6AA power pack to power the whole thing.