Rich. I think the rather reclusive CNC wizard JasonJack in New Zealand might have a machine for sale like the one he built for me but it is a bit smaller than the bed size you are thinking of. The one I bought is phenomenally accurate (I've used it to machine lenses the size of a pea with a brilliant surface finish) and very fast with servo motors and ball screws. I think I paid about £7k for mine. You could try emailing him [email protected] although he is building a house so might take a day or two to reply.