So having recently acquired a bass, I need an amp. I'm drawn to the light weight class D units for ease of moving, so I went to Guitar Center to check some out. I got to play a Rumble 500 2x10 combo and a PF500 head into a PF cab that appeared to be the 1x15 model. Volume wise, I was shocked that the Rumble seemed to destroy the PF. When set to the same level of master and gain, the Ampeg was noticeably quieter than the Fender. Is that due to speaker efficiency? Over or under rating power by the manufacturers? A defect in the Ampeg? I realize that there is more to the volume story than just numSpeakers(pi*r^2), but I'm at a loss to explain my experience. Tone-wise, I preferred the Fender but both were fine by me. They had some Markbass units too, but these are above my price range (looking at used units of 500+ watts).