A power supply upgrade would be the least cost option. This power supply would be better, but not ideal. This is about as much voltage that your drivers will take https://www.ebay.com/itm/NEW-One-Pie...FKL:rk:38:pf:0.

This drive along with a 70 - 80 V power supply would give the best performance. https://www.ebay.com/itm/DM856-Digit....c100005.m1851