I use OBJ but there is a bit of a routine involved. If Amorphium tells you it cannot open your OBJ export from Carrara, then process the file with UVMapper, selecting any map type and saving the OBJ with UVMapper. This will not change the geometry in any way. Now, the file should open in Amorphium. Check the "correct normals" box in the open dialog (not the reverse normals box, though), as sometimes the normals are messed up. Also, reversal of normals can happen when Carrara opens an OBJ exported from Amorphium. In that case, convert the imported mesh to Vertex Model form, and reverse the normals in the VM. A little awkward both ways, at first, but possible and worth the small extra effort.