Hi, I'm not affiliated with the guy in any way, but I thought I'd recommend the following stepper controller:
[
www.diycnc.co.uk]
Its not much more than 20 quid shipped anywhere, and I've found it excellent. It manages 1/8th stepping well, which I hope will improve the accuracy of my axes/extruder, and only gets slightly warm to the touch at 2.5A. While it suggests a higher voltage, it works fine at 12V at 10cm/sec on my heavy-axis darwin. Hope this helps someone,
James