i think the days of discount for cash are a thing of the past tbh... (not that i'll ever likely know as i don't have that sort of liquid asset)
dealers make money on finance, it is in their interest to sell it to you.
if you have the means, i would make out that are a finance buyer... perhaps pick a nice high APR and negotiate a chunk of change off the car. then when you pick the car up just say, oh i've changed my mind i'd like to pay cash please
that should suitably piss them off. hah!