It may be best to look for another more suitable motor than the 65v one. It's been a while since I had to figure this stuff out, but if memory serves correct, you should run between 3 to 25 times the motors rated voltage, 10 times being the most common used. Even at 2X, 130v goes way beyond any hobby driver.
following taken from Phil (PMinMO)
High speed torque increases as the ratio of the motor power supply to coil voltage increases. If your motor coil is rated 3V it will perform better with a 30V power supply than a 12V power supply. (If you want to understand that more, there is an excellent paper on Geckodrives website.) Bipolar drivers are more expensive, especially as the current and voltage increases. With that consideration, a Unipolar driver that is capable of higher voltage motor power supply, may infact perfrom better than a bipolar driver with a lower voltage power supply.
Ebay was flooded with these high voltage motors for a cheap price when I was looking for motors. The 4.8v should be a suitable motor. At 50v, your still within spec of the Gecko's. Another thing to keep in mind is if you reach the upper limit of the drivers, at fast deceleration, you will get a backfeed current that can be significantly higher than the drivers voltage specs. My own personal recommendation would be to get 3 motors of the same voltage (or very close) that way its much much easier to build your power supply to suit all of them equally.