... 6-wire motors can be used as unipolar (both middle-pins connected) or bipolar (middlepins ignored).
The RAMPS board delivers only STEP+DIR signals for a monolithic driver, for driving a stepper direct you doesn't need the RAMP Shield, a single Arduino with the transistor-arrays would do ... but you'll have to change the firmware for direct driving the solenoids.
But the easiest way is to use the motors in bipolar wiring with RAMPS and Pololus, adjusted to the motor current ...
The RAMPS board delivers only STEP+DIR signals for a monolithic driver, for driving a stepper direct you doesn't need the RAMP Shield, a single Arduino with the transistor-arrays would do ... but you'll have to change the firmware for direct driving the solenoids.
But the easiest way is to use the motors in bipolar wiring with RAMPS and Pololus, adjusted to the motor current ...