I'm probably going to eventually move mine onto a Real Guy. They have adjustable limbs, so you can make him as short as the short Buck. The hands need the most work to change how they fit. With the right neck adaptors the head is an easy swap, but will need gluing.
You can usually find the Real Guy on ebay for cheap. I bought half a case (6) a while back for about $100, I think.
The bodies look cheap, but have a great range of motion. They have less of a butt than the Buck though - not really an issue with Maul. I think Adam Hughes uses them for his customs.