Hi,
 
Have you ewer tried to connect a thick speaker cable to a DIN plug? It is not an easy task.  Monaco have some speaker plugs, that accommodate 
Ø 3 mm / 4 mm2 cables. As the plug use screws, you don’t need to solder the cable. Product name is CP-20.
 
Have a look: 
http://www.monacor.de/typo3/index.php?id=84&L=1&artid=3028&spr=EN&typ=full
http://www.monacor.dk/produkter/bilstereo-tilbehoerdiverse-1/vnr/141640/
 
Best regards
 
Nis