Pioneer GM6400F 4-Channel Bridgeable Amplifier 5

Pioneer GM6400F 4-Channel Bridgeable Amplifier 5 Like the other guys said - it is big, it is heavy. Big and heavy suggests big heatsink, which you want. I haven't opened it up to see how well built it is inside, but the bottom cover is made of that cheap, thin, plated steel that they make generic PC cases out of. In contrast, my 350W Rockford Fosgate sub amp is all cast aluminum and chrome-plated, thick steel. The Pioneer runs a bit hotter than the Rockford amp.