I have an sm-500 that I run mono into a four ohm 4x10 cab. I want to add an additional four ohm 4+10 cab. so that I have an 8x10 cab(two 4x10 cabs), but do not want to divide the power section of the sm-500 (250x2) because I will run out of headroom. Here is my question: how do I add an additional power amp, and still be able to run a line out to a mixing board? If I run a direct line out from the sm-500 into the input of a power amp so that each cab. is powered seperatly I will not have a line out to the house. Is a D.I. the solution? Does anyone here use this setup?