Best way to travel from Athens to Istanbul?

[NoTurningBack]

I am traveling Europe this summer. I will be in Athens and the Greek Islands in June and will want to make my way to Istanbul. So far the most feasible option is train or bus from Athens to Thesaloniki to Istanbul. This a long trip though. Airplanes appear to be too expensive (close to $200).

Does anyone know of how to take a ferry from one of the Greek Islands to Turkey and then a bus to Istanbul? This seems like it could be quicker and more fun. Anyone have experiece with this?

Also I am planning to take the Bosfor Ekspresi from Istanbul to Bucharest. Has anyone done this?

Thanks!
Nate