Using the same program I see 52 idle and 62-64 while gaming.
One important note, if you have a graphics card that has the fans turn off at low temps, you might want to shut that feature off. Even at the lowest fan speeds, some minor air flow off the GPU down onto the PCH heatsink really drops the PCH idle temps down. For me turning of the 0DB feature dropped PCH idle by 11c.
Open case or not, with zero airflow over the heatsink area, your PCH temps will higher. In an open case or on a test bench, with zero air movement you can expect your PCH to run on the higher range of temperatures.