The bass management switch only matters when using the 5.1 analog input - it has no effect in the digital inputs or on the stereo analog inputs, so the position is irrelevant. The bass management settings in the 950's menu will determine how the digital audio and stereo analog signals get processed.

Since you have a Blu-ray player connected to the 5.1 analog input, I'd recommend setting the bass management switch up to the "On" position and setting the speakers to "large" in the player's setup menu.