Dude, you know when "it's time" to sell your car. I am selling mine, too. It's "just" a 94 GT. (automatic, at that) I haven't really lost interest in it. I'd just like to try something different. Nothing wrong with that. To move up to a Bullitt, is a good move. Will you miss your 95? Absolutely! Will you get over it? Absolutely! If it REALLY means a lot to you, you'll find a way to get another one. That's where I am. I had a 1985 Merkur XR4ti that I absolutely LOVED. I am going back to those, when my GT sells. It turns out that it meant that much to me.
Like others have said here, you are going to have a heck of a time not taking a beating on it, pricewise. Hold out for the guy that is willing to pay what you need to get for it.
My vote is to GO FOR IT on the Bullitt, you probably wont regret it.