Hi,
Have you tried Cura? It can read a .AMF file, convert it to G-code, and send it directly to your printer, I think.
But I think you're pretty close to the leading edge of the technology with a 5-nozzle printer. As such, it will be difficult to find anything that robustly supports it. You'll probably need to contribute to that development yourself.
You will need to use some other program to generate the original model though. There's not many 3D design programs that support .AMF yet (OpenSCAD, Blender, SolidWorks) .
Frank