I agree. Prague won't work if you intend to drop off the car. Beyond that, I can't really make my mind up about what to suggest to you. If it were me, I'd probably go to Bamberg. It is a beautiful town, and the beer is indeed delicious (sorry Radeberger). From there you can take a train or drive (and drop in Berlin, no big deal). The A9 Autobahn is very good (and the newer sections are smooth as a baby's bottom). Dresden is definately worth a visit, but you could perhaps achieve a taste of this by doing a day trip (via train) from Berlin. Does your schedule allow this?