It would increase speed if it was a Sepex motor as the new controller probably has a lower Field voltage setting.
On a Series drive You either have to increase the overall voltage at the motor or reduce the Back EMF flux intensity by doing a "Field Weakening" shunt.
I think the other important aspect of the high current controller is that You have very granular control of that additional torque.
You can always add a 100HP NOS shot to your truck's engine, but it would not be very practical to pull Your boat out of the water (it could be entertaining though
)