I am looking for a 12V Dual Motor Controller that can supply at least 5A per channel for two 12V motors, and that can be used with an arduino. Do you know of any product with those specs?
Yes, there are several products that can independently drive two DC motors at 12 V and 5 A, which can be used with an Arduino.
OpenCircuits has a list of motor drivers, some of which meet your criterial.
Sparkfun carries many motor drivers that meet your criteria, including the "Monster Moto Shield", the "T'Rex Robot/Motor Controller", and several Pololu drivers.
Robot Power carries many motor drivers that meet your criteria.
Have you heard that shopping questions are off-topic on this site?