one lead screw or two

[johngoodrich]

might just get an extra motor and ballscrew then

[Jonathan]

might just get an extra motor and ballscrew then

...and stepper driver.
It's probably easiest. The extra power from the second stepper can't hurt either.

[E.V. MacHine]

Same lines I'm thinking along. Means dedicating an extra axis, though, and I'd like to have the option of retro-fitting a rotary axis (sometime) later - so a 5-axis system, then? It'll need a 5-axis break-out board, to start with. (How do you add more axes? Does it need another com/lpt/usb port; EMC supports up to 9 axes, apparently... ) and a separate driver for each motor. And that's it??

'xcuse me chipping in, hope it's okay...

...cheers, Eric.

[Jonathan]

[QUOTE=E.V. MacHine;23456]Same lines I'm thinking along. Means dedicating an extra axis, though, and I'd like to have the option of retro-fitting a rotary axis (sometime) later - so a 5-axis system, then? It'll need a 5-axis break-out board, to start with. (How do you add more axes? Does it need another com/lpt/usb port; EMC supports up to 9 axes, apparently... ) and a separate driver for each motor. And that's it??

Yes that's right, driver and motor for each. Unless you drive both the X screws with one motor and some timing pulleys / belt.
The parallel port has enough outputs for 6-axis if you don't use them for anything else, such as spindle control. A 5-axis breakout board is probably your best bet...