The way that it usually works is... A head can run one cabinet at 150 watts... or two cabinets in stereo at 75 watts.... this obviously means you split the output between the two cabs... The advantage of having a stereo head is that you get to hear the full effect of your effects pedals... If you run 2 cabs in mono configuration the same sound comes out of all the speakers... If you run 2 cabs in stereo you'll find that when you have a flanger on that's set to pan left to right... that it, in fact, does pan the sound from the left cab... then slowly into the right cab and back and forth. It's more for effects junkies than anything... So, if you like effects... I'd say the advantage is enough to pay the extra cash... but otherwise... I'm indifferent to stereo cabs... I don't use many flangers, phasers, echos, and all that stuff... just a little delay, overdrive, some wah, and such... basic stuff... so I never felt the need to go buy a stereo head.