If you have time in Berlin, take a side trip to Potsdam. The palace there is simply fabulous and the park that it is in is filled with all kinds of beautiful constructions, sculptures, you name it. The town is nice too and if I had an extra day, I would just stay there and walk around. They are rebuilding and renovating like crazy. The Dutch quarter looked interesting too, though they were having a Dutch fest when we were there last April. We went with Insider tours to Potsdam and also used them to go to Sachsenhausen Concentration Camp. They do a wonderful job of explaining everything and the price was only 15 €. Their tours of Berlin are also wonderful, though I would recommend going to their website, since all the information about them in the Rick Steves guidebook is completely wrong. www.insidertours.com
I also think Dresden is a good idea. Have not been there, but it is way up on my lists of places to go.