.max and .rmx are actually backups of the rmf and map files created when you save the map or rmf. (Thanks to Seventh for this vital information which saved the compo map of yours truly
). The real irrelevant files created on compile are the .p0, .p1, etc, .wic, .lin, and .prt files. DXF is a format used by many 3d modelling programs, like Maxon or MAX. You could probably make a map in one of these programs, I'm skeptical on it's playability, in terms of both scale and speeds, however.