A CNC machine looks like overkill, if you want to create only a few loudspeaker enclosures. But if you have more milling in wood or aluminium to do, it is an interesting tool.
After reading some discussions in different CNC forums, the CNC 6040 might be an interesting machine to look at. For sure, there are lots of other interesting machines available. Therefore make sure that you first understand your requirements before selecting a machine.