The Rex II definately looks like an incredible piece of gear and given its new price tag of $20, 000, your asking price makes it an outright steal. I just don't think that many people have the disposable income they used to have and the ones that do are being more tight fisted with it because we live in an uncertain economy/future.
If I were you I would restart the ad with its new lower price because most audiophiles are looking mostly at the first two pages to see what's new on Audiogon. This would increase exposure.