There are loads of hotels down the hill from the Sultanahmet area and the Cosmopolitan Park is a fine one. The location is terrific, around the corner from the Blue Mosque. The staff went out of there way to be helpful and friendly, including getting us breakfast out of the usual times. The view from the outer rooms and the breakfast area is breathtaking. I would stay there again in a minute.
That said, there are several things people should know. None of the hotels in the area (except the Four Seasons and maybe Yeshil Ev) are first class international hotels. The rooms are clean but small and some things do not work right (shower door off the track). But for under Euro 100, this is a fair price. I have run into this standard across Europe and my budget does not support a Four Seasons room.
The biggest drawback of the Cosmopolitan Park (and maybe others) is that there is no elevator. The staff will carry your baggage but you need to climb to the fifth floor (European counting) for breakfast and to whatever floor your room is on.
If you are looking for a comfortable place to stay in Sultanahmet, the Cosmopolitan Park is a fine choice.More