g320 or g340 for mill setup?

Heres my deal: cnc for a 10 x 40 american knee mill.
Im at the point of selecting timing pulleys, encoders and gecko
drives. I have .200 lead X & Y.My thought on setup is as follows: A
2:1 pulley ratio, 250 cpr quadrature encoder,gecko g320 and mach1/2
nc software. my calculations tell me 1 pulse = .0001" so at 25khz I
should get a rapid of 150. is this resolution too high? should I use
step multiplying or diferent encoder combo ? Any input would be
appreciated.
thanks--mark