Not sure this could be done stereo out, as I remember this was done with a stereo pan, one amp (expression pedal) toe up 100% and the other amp tow down 100%. The expression pedal blends the two amp models based on the pedal position. Like using the expression pedal to increase or decrease gain but with two different amp flavors. I will try Tagmuse's suggestion and try the merge-block. Thanks all...