Quoted from cosmokramer:powered subwoofer is another fine choice
My MET still sounds tinny compared to ACDC when hooked up to the same polk subwoofer. I think with MET, the cabinet speaker is not producing decent enough midrange which the sub isn't going to help with much. ACDC on the other hand has a 12 inch cabinet speaker and has far better midrange - it's not even close. The sub is the icing on the cake, but I think something is still needed for midrange on MET.
Rob