Sieg X3 or Warco VM-16?

I want to buy a small bench mill for conversion to CNC and am
considering either the X3 or the Warco VM-16 (aka AMA20). Is it as easy
to add ball screws to the VM-16 as the X3? The VM-16 has a larger
table/work area, but only has MT2 spindle. The X3 looks heavier and
sturdier. Otherwise they seem very similar. Any recommendcations,
including where to buy? I've seen the VM-16 type on eBay for £650.
Thanks,
Andy.