Victrons next Orion XS is 1400watts, which I suspect would be more power than I would want to take out of my current alternator, Not sure of the cost yet, but would be surprised if it were twice the cost of the 50amp, so around £500? I think I can go up to a 210amp alternator using Iveco parts, which is still a bit too small at 12v for that (and actualy gives lower output at lower RPM than my existing one IIRC). I guess if I were to fit an aftermarket (for me) 24v/48v 2nd alternator, that would be a handy piece of kit, but by then quite expensive. My next upgrade will be 920AH Lithium to go with the 550w Solar and Multiplus II we aleady have, but I'll probably leave the B2B at 50amp. After all I don't necessarily need to fill the batteries, just add enough for the next stop.