I went down that path years ago with my 17-20 xmtc machine. There are several ways you can go;
1. DC motors with a controller and pot control for speed. The problem is finding one that has the right rpm and power for driving the table. Most of them run at pretty high speeds- about 6000 rpm- requiring a lot of gearing down to get a reasonable feed rate on the table.
2. DC gear reduction motors- these will get you the power and speed you need, but because of the gear reducer, it makes turning the handles by hand very difficult.
You can look at www.surpluscenter.com for low cost versions of the above.
3. A stepper driver ( chopper driver) and a stepper motor offer the type of RPM and torque you need and will bolt right up to your existing mounts. You can Google search them and find a lot of fairly inexpensive units out there. If you want to run more than 1 axis, then you will need to buy 3 motors and plug in the one you want to use.
HOWEVER- most of these drivers are very sensitive to what is known as an inductive spike. If you unplug the motor while the power is on, it will blow the circuit. So going that route, plan on some day forgetting to turn off the power and popping the board. It would seem that you could wire in a 3 position switch to select among the 3 motors, so no unplugging is necessary, but it requires a special switch called a ]make before break] to insure that the circuit is always completed during the switch over.
For a Tripower or Patriot size machine, you will need a driver with a minimum of 3 amps output and NEMA 34 frame size motors in the 350-400 OZ / IN torque range.
BTW- if your hand cranking is too hard, you probably adjusted the anti backlash nuts too close- anything less than 0.004" lash will start to be very hard to turn.