Well, my friend and I decided to follow Ctein's recommendation on Luminous Landscape to use "printer manages color," and guess what? The color is much improved, though it is still not an exact match of what is seen on the monitor. The monitor, BTW, is an old Apple 23 inch Cinema Display, which has a narrow color gamut. Perhaps that is the limiting factor in trying to perform accurate soft proofing in the ProPhoto color space.
Rob