If I were you I wouldn't give them another number until they countered your initial offer. Let them know that you are gonna buy a car either way (since you like that black car which is a year newer and around the same price). Let them know that only a fool would buy a car by the sticker price and if they're not willing to negotiate then you'll take your business elsewhere. Bet they will change their tune. Make it seem like you felt disrespected that they shot your initial offer down without even countering