Not really sure what you are meaning, if the dips are set to 256 then you would need 512,000 steps per unit in motor tuning but that would be crazy and you would only get a few IPM for rapids
I suspect you may be reading the dip switches wrong and if it is giving you accurate measurements ie when you command a 1 inch move it moves 1 inch then all is good
Not sure what kernel speed you have Mach set to but if you are at 25KHz and finding the 16,000 steps per unit are limiting your rapids then you should be able to increase to 45KHz kernal no problems, most computers/parallel ports can handle that. Also set your pulse widths to 2 or maybe even 3 on the motor tuning page as I think these drives require a slightly wider pulse.
And lastly no worries about being new to CNC, we all were at one time and we are all still learning
Hood