Planting vaughns makes me curious what state you live in. I have many failed attempts, at many different varieties of Bermuda. Haven't tried vaughns, but I thinks it's more suitable for my climate than some I've tried. Ditto on the crabgrass.
I would suspect the only reason to try and kill the crabgrass would be for the horse hay market. Otherwise, hands down the best summer grass I can grow in GA. Cows will walk past the BMR pearl millet to eat the crabgrass. Nobody's nose knows like the cow's nose knows...or so I've heard.