I have a Rover 5 with 4 motors/encoders and use the Dagu 4 channel motor controller. I use the current sensing feature of the motor controller. Powered from a 2S Lipo at full PWM the motors draw about 1A /motor when turning left/right (when going forwards/backwards the motors draw less current). Stalled these motors draw over 3A a piece. I have used a cheap L298 board from Ebay on another robot and have taken a good look at the datasheet of the L298 chip. There are some things you need to take in to account. If you are pulling 1A from one channel of an L298 you will have a voltage drop of 1.8 - 3.2V on the output. That also means that a serious amount of heat is wasted in the L298. You need a big heatsink to dissipate that heat. The Dagu 4 channel motor controller uses fets with a very low RDSon, so there is only a tiny voltage drop. So no power is wasted and a heatsink is not necessary. The Dagu controller was especially designed for the Rover 5 and is rated for 4A stall current / channel.
Here is a photo of my Rover: http://www.bajdi.com/?attachment_id=623 It's my "development platform" 