I saw the RPM vs. power stuff you were talking about and chose my replacement alternator because it made good power at lower RPMs. But, mine was still right on the verge. If the car was idling properly, my 3G with underdrives would make enough power even with the e-fan on. But, if the car had issues and the idle started hunting around it would sometimes drop below the threshold and make things worse. Going back to stock pulleys kept the car from stalling as things weren't quite right with the car and I chased my way through the idle checklist. To be blunt, I think underdrives suck, 3G or not.
