The BG-120 is definitely a step up from the BG-80. I used the BG-100 a few years as my practice amp, and I also ran a PJB head with two C2 cabs. Even with that setup, I still feel that bigger speakers just sound fuller and move more air. That’s subjective, but my 12 and 15 inch combo amps definitely give me more low-end presence than the smaller PJB drivers.
I sold all my PJB gear because I prefer bigger speakers and the voicing of certain amps. Fender, Ampeg, GK, and Aguilar are my favorites. The Fender Rumble 40 is really great for the price, though I still wouldn’t say no to an old PJB briefcase amp. 
Show us your amps is a great thread if you want some inspiration!