Stephen Hawking?
Yes, it sounds like him. Even in German.But he is brilliant. If someone knows the right way it´s him (Is that correct English?).

You´re right. Mplayer sounds better.
I´m using Navit, too. A great app.For free and powerful.
The next thing i will try is to use mbrola voices with espeak. That should work. Packages are available.