I might be misunderstanding here so i want to make sure i understand your signal. Baritone guitar with a G as your lowest note, that being the same G that i play at the third fret of my standard 4 string bass. You then split the clean signal into 2 effects chains, with one of them gong to a mesa carbine bass head and including a pog that adds 1 octave down. How much volume are you looking for from the cab getting this signal, is there a crossover keeping the high end, 2.5k and up, or if this cab? I'm thinking you definitely want to go tweeterless. Our at least make sure the tweet can be turned off. I might think about an older mesa diezel 2x15. Or a powerhouse 2x15.