I've not used motors this large yet, though I own a pair as part of a mobility chair transaxle assembly. I do have a word of advice:
Purchase a controller, don't attempt to build your own as such a controller for large motors isn't easy to design. Unless you have this experience, of course, your time and money (and sanity) will be far better spent on other aspects of the robot. Just note that such controllers are far from inexpensive (but likely less expensive than something you could design yourself - unless, like I noted, you have experience in such design work).
Good luck with your robot.
