Alan's PicStep board would be a pretty good choice for your application, although I wouldn't recommend running it at 55V, becuase your motors will produce some back emf. Enclose the boards and electronics in a metal enclosure and you should be ok.
At 40V you would b 10 times the coil rating and will get pretty decent performance, not Gecko quality, but you wouldn't have Gecko dollars in it either.
Phil, Still too many interests, too many projects, and not enough time!!!!!!!!
Vist my websites - http://pminmo.com & http://millpcbs.com