Most hotels in Berlin are located around Kurfürstendam, close to the city centre and not to far away from the venue. I have booked hotel at Hotel Kurfürst, right next to Kurfürstendam. As BV said the public transport is great, and in the worst case scenario you can even walk the distance. But after a concert I guess you're a bit tired, so just take the U2-line from the Olympia Stadion back to city centre.
For a list of hotels:
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www.bookings.de]