Well the Mesa Mark IIC+ begat the SLO, and the SLO begat the 5150 & Dual Rec, and finally the the 5150 begat the 5153. EVH teamed up with Peavey to create the 5150, which was intended as a poorman’s SLO (which he had just used to record the F.U.C.K album) because he knew that Soldano would never be able to produce a signature amp in the quantities and price-range that Peavey could. So the 5153 is in many ways a modern version of the SLO.