These servo motors worth a darn?

Got a question or two. I have a 3 axis cartesian coordinate robot that I
am reconfiguring as a gantry robot. it's got top notch hardware like NSK
linear ways and preloaded ball screws. Came with some Tamagawa brush
servo motors but no amps. The robot was an Apollo, appears to have been
made in the UK. All I have for specs on the motors is wattage. Two are
100 watt with 500ct encoders, one is a 60 watt, and there is a large 200
watt with integral brake. I can provide model numbers if anyone has ref.
material.
I'd like to know if anyone can guess what sort of power output I might
see out of the 100 watt motors, both peak and average.

With 10mm pitch leadscrews, if I use 1000 line quadrature encoders, and
if I understand what I've read here, I ought to get a potential .0001
resolution. Is that correct? Due to design, I'd really like to belt
drive the screws. Can I put the encoders on the end of the screws or
would that introduce some sort of servo error?

Will be back with more questions soon as the Glen-Tek servo amps I got
on Ebay arrive... (like, will they drive the Tamagawa motors...)

Jon