Keep in mind: You will never have as much leverage as you have now. If they don't offer you enough to stay, they lose all institutional memory of the entire department. If they don't treat you well enough to be happy, they will have to scramble to find someone to replace you when you inevitably move on. No matter how shitty the promotion, it's still a promotion and looks great on a resume. Share your concerns (politely) and come up with the amount and conditions that will make you stay. Ask for them. Buddy of mine switched from a small boutique agency to CAA; his wife was insistent that he ask for "fuck you money" because she knew he'd burn out after a few years and they needed enough of a cushion he could take a few years off after that. He got "fuck you" money.