They all want me to give a number but I really have no idea what kind of number is suitable. I'm thinking six figures. But is seven figures out of question?
I'll just go out and a limb and say they both are. Your interested buyers are likely hoping for a much smaller sale; domain names aren't quite worth what they used to be.
Test the waters though. Email each buyer and tell them to throw out an offer because you've got other suitors. If you start mentioning six figures I promise you you'll scare them off. You're always welcome to lie about the offers you've gotten to raise the price to a certain point, but if you start too high people won't bother.