How fast you can go is mostly determined by the machine itself - motor torque at speed, reduction/screw pitch, etc. Acceleration is probably the first thing that will limit 3D performance. How is your machine setup? Motor size, belt/gear reduction, screw pitch, supply voltage/current, motor controllers, microsteps, etc. What settings are you using right now for max speed, acceleration, etc.? What kernel speed are you running?
Regards,
Ray L.