thanks for the replies 
i need to run the motors both forward and reverse,
the motor current is 7.75A at full load and 12v, so i will need something that support up to 8A, do you know something like this?
(this is the motors that use : http://www.ebay.com/itm/RS-550PH-Motor-12V-DC-14-100-RPM-High-Power-550-Size-DC-Motor-Nichibo-/280976231186?pt=LH_DefaultDomain_0&hash=item416b7d0b12)
there is a motor shield the can move the motors both forward and reverse and can support 12v (from extrnal power source) and 8A ?