Asian Lathe Conversion

I'm considering purchasing a 12 x 36" or a 13 x 40" gear head lathe
from Grizzly or Enco or ???

Has anyone had any experience with retrofitting the lead screws with
ball-screws on either of these machines?

Also, any comments on the quality and/or accuracy of the Asian Lathes?
I found one Review on the web that claimed a quantum leap in quality
from the smaller to larger machines.

I assume that they are no match to American or German machines, which
I just can't afford. Nor do I want to take the chance with used.
However if I find that I have to tweek, tweek and tweek just for +-
.001", It would probably be best to do without.

Tom M.