Further explanation: My band is a two piece metal band, I frequently use the Spider IV's looper capabilities to fill in for...pretty much the other "half". I simply want a deeper tone like running a bass amp at the same time. I could just add more bass to my normal amp, but I pretty much have a decent bassy tone without it destroying my lead tone. (I hope that's making sense haha)

EDIT: Also...I just realized that because I use the FBV footboard, wouldn't the loop signal only carry on the guitar amp and not to the bass amp while using the A/B/Y switch?