Definitely go with the lmd18245 if you can afford it. The lmd18245 is much better at dissipating the heat. It has better specs and can withstand 6amp surges. It has a 12-15amp burst rating as well. Here is our designs, very reliable.
http://www.embeddedtronics.com/microstep.html http://www.embeddedtronics.com/microsteppld.html
Not open source but the code is posted as well as the schematic, design is proven. Boards are professionally done and are available if you find it too much of a bother to layout your own.
Kin Fong