Control of 6 12VDC linear actuators with Arduino Mega

I'm currently working on a project that needs independent operation of 6 linear actuators. I was planning on using an Arduino Mega with three motor shields but after looking around I can't say for sure if its possible to have three motor shields coupled with the Mega. I just want to make sure that it is possible before purchasing the shields. I have seen independent operation of 4 motors using 2 shields with some pin trimming.

The project is just extending one of the actuators after sensing a corresponding input and then retracting. So I need 6 pins available for inputs as well.

The current draw of each actuator is 2A and they are 12V. Only one actuator will be moving at any given time and I don't need to use PWM as they will be used full speed each direction.

Thanks

You should be able to operate the actuators using two 8 relay boards like below (four actuators per board)

http://www.ebay.com/itm/New-5V-8-Channel-Relay-Module-Board-for-Arduino-PIC-AVR-MCU-DSP-ARM-Electronic-/270984095956?pt=LH_DefaultDomain_0&hash=item3f17e928d4

I'll check into that, thanks for the response. I'm relatively new to the whole Arduino world so I'm not as familiar with all the add-ons and options that are available to do this. The other option I considered was just building a circuit with all the necessary transistors and H-bridges but I would rather avoid that if possible.