So what is the best price/performance card that is reasonably available?
I'd go for a card with buildin monitor switcher, like the CyberVision64 or a PicassoII. If you want to use a modern monitor that can't display 15 Hz screens, I'd go for a Picasso IV which has a scandoubler as well, or get a scandoubler to suit the before mentioned cards in case a Picasso IV is out of the question.