Thanks Gents.
I should probably elaborate a bit. I'm an owner as well as an employee. Our company is tiny. Two owners and three employees. Myself, my partner and his wife. In essence, I'm what's being bought. I wrote every single line of code, deployed every byte of information, have been involved with every single client and the entire thing would fall apart in under a month without me. My partner has been only peripherally involved over the past few years. He's been working on other projects that are not part of the sale. His wife does our office management and the majority of our light support. My partner has not been offered a position with the new company. Myself and his wife have been.
There's no deal without me - literally. If I don't take the job the deal is off and that's understood by all. I'm dealing from a position of strength but I intend to be completely reasonable in my negotiations. I don't want to sour the deal. I want to shed ultimate responsibility and the stress that goes with it. We're internet based and you may not believe this but I've been on call every minute of every day for the past ten years. Middle of the night, weekends, vacations, everything. I'm worn to the bone.
The aggregate of your responses lead me to believe that, given my circumstances, my tenure with my current company should be strongly considered transferrable.
lesson: don't count on anything
That... I can count on.