The S-15Bs are beefy. I was running S-15Ds with EV speakers, which each weighed just under 50 pounds. Because of their size and handle placement, if you carry them hugged close to your chest, they're really easy to move. The Bs might be a little bit more work, but they should have more going on in the low end compared to the Ds, which roll off at about 50 hZ or so.
Why do you need an upright rig for your studio? That rig is ideal for stage use IME, but my usual practice is to run through a Fishman EQ into a Countryman DI, which is a lot less work to carry around than 100+ pounds of amp and speakers. Just a thought.