Ok, so is the limiting factor the ramps? I want to be able to take advantage of the bigger motor, but if it cant get the current then there's no point.

When you say slow, do you mean it has a limited top speed, what about accelerations? Can I at least hit 1500mm/s2 or about the equivalent of 250 mm/s out of it? (using standard 3D printer pulleys etc...)

What is CBA?