About 40 amps I'd say . You can get the same machine in two different amperage and the only difference will be the thickness of material it will cope with.
and the tickness of the mig wire at 160 you can go 0. to 0.8 with 200 amps you can use 1.0 wire. Another thing is the fuse on you instalation 160 a 16a will suffice on a 200 amp a 25a is recomended.