Actually I'm in work on a expanded version of the AVR board on the first post. 100V, unipolar, heavy current (can't say yet, the FETS are more capable than the board will be) microstepping. The unipolar will come first as the hardware is almost ready to order protoboards on. Microstepping has been the hurdle to implement in a low cost, KISS design, but that too I believe is not an issue, at least to 1/8th step.
Also in parallel is a bipolar design.
BCwandererer, I'm familiar with the 2010, 2104, etc. Right now I'm playing with P channels on the top side though. Their simpler, their cost too implement is less, 120V 14A Pchannels don't cost much these days and their pretty robust.
Both designs are limited to 100V.