The Gecko G540 is only rated for 50v, and a max of 3.5A per axis. Do you have the current limiting resistors in your stepper cabling per the Gecko documentation? Exceeding its ratings is what would "blow" the Gecko. I use a Meanwell 48v 12.5 A power supply (SE-600-48) and have not had any problems, but I am only running NEMA 23s.
The Leadshine MX-4660 will handle 60v and up tp 6A per axis and can be used as a drop in replacement for the G540 if the G540 is being overloaded.