What is your budget for the stay? There are plenty of great places in the centre. A reasonable priced place is http://www.parkinn-berlin.de/. Do not expect too much (you cannot expect a lot from the places you mentioned) but this location is on Alexanderplatz and it is one of the few high rising buildings in the centre. Alexanderplatz is at the far end of Unter den Linden Boulevard, however still in walking distance to several of the tourist attractions like the Cathedral, like Hackerscher Markt, Nikolaiviertel.

Most important: It is (a) on the U5, the tube going directly into Friedrichshain and it is maybe three stops into Friedrichshain and it is (b) on the S-Bahn going to the West and further tube lines and trams - perfectly located as a base camp.

As said: It is Holiday Inn style but view and location are great.