I'm working on an interrupt-driven monitor for the DS89C450. This makes it possible to run a task and monitor/ change variables etc..
I recomend ad 22.1184 crystal in combination with the in the mcu build in clock-doubler. 44 MIPS makes it a superfast MCU.
For the steppermotors you need for at least 3 x 4 = 12 pins, the 89c450 has only 10 direct i/o-pins, I prefer memorymapped i/o, this makes programming very easy, because all the port can be accessed like normal memmory location. I'm very interested in a 3 axis engraver to use it for the prototyping prints and experiments