Okay, for the rack-mount versions of both heads: There are a few extra sliders, and the tube section on the ABM... same power output etc... Here is my question: The Mag weighs about 20 lbs.. The ABM weighs in at 30 lbs! Everyone give your opinion as to what you think gives the ABM 50% more weight... Is it a thicker case? Is it a ten pound tube pre-amp? Is it filled with gold coins? creamy nougat?? who knows!?!?