Using the Xcontroller will give you same max rapid, but the available torque at speed will be greater on all axes, especially on the Y-axis where two steppers share one driver.
Greater torque at cutting speed = increased reliability / less chance of loosing steps.
If larger rapids are desired, then you need to increase the PSU voltage.
If you want a key-ready match to the XCarve get the Xcontroller.
If you want a controller than will outlive the Xcarve or provide more power then get 4x Leadshine DM556 and a 48V PSU.
I use Nema23´s (269oz/in2) @ 48V with DM556 and DM856 on my 1605-screw machine, if I try to hold back the gantry by hand my machine will slide on the table before loosing steps. (its about 140lbs in total)