Step motor &control for CNC router

[hanyupingen]

I'm going to start building a CNC 3 axis cutter/router/etc machine over the next few months. I'm happy enough with the mechanical side plus I've found a HEX image for the Arduino that turns it into a Gerber device and controls the three steppers.

What I'm not sure about and what I want to avoid spending too much on or buying the wrong stuff is the stepper motors/control boards etc

I've not used stepper motors before but I had 3 tiny motors and 3 control boards that came with my original Arduino years ago. I've messed about with them but clearly, they are just toys.

What I'm looking for assistance on is what size motors I'm really going to need. I'm seen a video of a CNC 3 axis machine about the size I want to build which used 3 Nema 17 motors and I've looked at these on Ebay but there are lots of different ones with different specs. I'm hoping to be using a 1/4" or 3/8" router as the main tool but will be building it capable of changing the head for other devices.

Any pearls of wisdom ?