C545 is right across from the crew only stairs. It really didn't bother us because hardly anyone used it except for delivering/picking up luggage at the beginning/end of the cruise. It is a great location for emergency exit.
The cabin is at the end of mid-ship area and the Casino is below. No public area above, just more cabins. It was quiet and you didn't feel a lot of rocking when the sea was choppy.
C545 is about midway between the forward and aft elevators.