In 'pro audio equipment' you will find under 'McKenzie blah blah..' 4 x 10" loaded (ie with drivers) mid horns. Cabs are modelled on a well-regarded Speakerplans design with good track record for SQ (the MT122 from memory). Look wellbuilt and a good starting off poinr for anyone following the 5 way horn threads in DIY section. With 2" compression drivers on top and a couple of bass bins (folded horns, say 15") you would be well on the way to semi-psychosis status if not quite monster loony. You need 2 so sell the other two on..
Jack
Jack