Well, problem solved. But not without another road trip on my part.
One of the church members donated the money for two new PV900s. I drove back down and wired them in on Saturday. To the surprise of all (me, mostly) everything works, and amazingly well given the decades-old speakers they have.
It ended up not being as big of a PITA as I anticipated, though it was still bad enough. I had to redo all the cable ends, changing them from 1/4" to Speakon. (I like the Speakons, by the way. I first thought they were going to be a nightmare but turns out they are pretty slick.) The real test of my patience was trying to redo all the cables while scrunched into the backside of a desk-turned-sound-console and being slowly roasted as temp in the cabinet climbed to somewhere around.. oh.. eight thousand degrees or so. Trying to strip and solder connections in a 2x2 box without burning yourself, sticking a protruding nail into your tender flesh, knocking something important down the access panel in the floor, or dripping sweat into the rest of the equipment is quite a feat.
But, hey, now they have all the mono surround sound the members are too deaf to hear.
Brad