oh yes the 18s are punching below the belt for sure..i tried it at rehearsal and i liked it a lot,thats one 300 watt jbl mr 818 cab so im going to recone the other one and try two 18 inch cabs on the bottom end and my 4x10 on top.i moved the crossover frequency up to around 2-300 hz ,this helped a lot.also im now just using the warwick power amp to drive both cabs, i have retired the marshall valve power amp because i can get a bit of grind if i want it from my ampeg preamp and its one less thing to transport.obviously this is a primary consideration if im contemplating dragging 2 huge 18 inch cabs to gigs but hey i like it what can you do?