Thanks for the reply, Peter...
Each radiator in the house has a self-bleeding valve for adjustment: the ones upstairs are virtually closed and the ones downstairs are fully-open. That self-bleeding feature is what makes them hiss so freakin' loud at the quietest parts of a movie...
All the plumbing guys that have been here over the years (that I've asked) basically say "it seems like a big area for just one radiator".
I should mention also that this would probably be a sizable factor in dealing with our "frozen pipes" issues above the kitchen, though there ARE less expensive ways for us to deal with the pipes specifically... (though the kitchen would still be cold with any of them....)
