The closet major hotel would be the InterContinental Berlin Budapester Strasse 2, not one of the chains you mentioned but a decent hotel is Alsterhof Hotel Berlin Augsburger Strasse 5, it is much closer to the heart of things, then Golden Tulip Hotel Hamburg Landgrafenstrasse 4, a few blocks from gay central, and very near the action Hotel Artim Fugger Strasse 20. And as previously mentioned the Best Western Hotel President An der Urania 16-18 is close by too.

As for the majors, Swiss Hotel is not too distant, bit further out is Grand Hyatt, Holiday Inn Garden Court, The Hotel Palace (LHW), that should give you a pretty good start or at least I hope so

Sam