9 Nights - Southern Germany

"Also, we are wanting to visit southern Germany, including areas in the Black Forest, the castles, Munich and 1 day in Salzburg. Any suggestions on cities and villages to stay along the way and overall trip plan?"

Sure. First off, "The castles" you refer to...?? When you are in Bacharach, it's not just about the cruise; you are in Castle Country there - so spend a little more time there than you planned and don't miss out on the real thing.

Rheinfels - just 10 minutes from Bacharach
Marksburg - across the river from Bacharach and north a ways before you reach Koblenz
Burg Eltz - which R. Steves claims as his favorite castle in Europe
Reichsburg - in fabulous Cochem on the Mosel River near Burg Eltz

All can be toured. Reichsburg also has a terrific free-flight falconry show. All are real castles that have stood - or in some cases fallen and stood again - for 700 - 1,000 years.

Sadly, the only "castles" that most first-time visitors to Germany have in mind aren't castles at all; Neuschwanstein, Hohenschwangau, and Linderhof, King Ludwig's digs south of Munich, are all late 19th-century palaces. Maybe those are where you're planning to go. They may be worth visiting if you can handle the crowds there, but castles they are not.

Black Forest: Gengenbach, Haslach, and Schiltach can be excellent base towns and are very nice places in and of themselves.
Gengenbach
Haslach
Schiltach

If you are planning to visit Neuschwanstein and Hohenschwangau, which many people call "the castles" even though as the previous poster said, they are 19th century palaces, I think Fuessen is a good place to stay. Fuessen is a nice, pretty town with enough to see for an overnight stay, and there is a short bus ride right from the Fuessen train station to "the castles." I think especially Neuschwanstein is worth the visit, not to see an authentic castle, but to see something else that is, well, unique and interesting! It is crowded, though. Definitely take some time to tour some of the older, authentic castles along the Rhine if you are interested. With 9 nights, I probably would spend half the time along the Rhine, go to Fuessen for one night and then Munich the rest of the time, skipping the Black Forest for this trip. Salzburg is a good day trip from Munich, though it is also worth a longer visit.

If you have time, a visit to Hitler's Eagle's Nest near Berchtesgaden affords a magnificent view along with some historical importance. At the Hotel zum Turken in Berchtesgaden, there is a "bunker" left over from the Third Reich days that you can visit. It's the real thing, not a tourist reconstruct. The small town of Mittenwald is the best Bavarian town I have visited to date--I've traveled through southern Germany three times and have yet to find a town as scenic. In Munich you might want to try the Nürnberger Bratwurst Glöckl in the shadow of the cathedral. Pay attention to the first posting re: castles.

Looks like you have some good tips to get you started. Since you have the car to make it easy, I think you will enjoy including the Wieskirche and Linderhof, near Fuessen, as well as a luge ride.