What sample rate should I choose?

I have a MacBook Pro with an external hd with my music on it. Some 24bit/192kHz, 24/96, 24/88.2, FLAC, 44 and 48. When I feed these files to my DAC, Wadia 321, should I be going into the Audio MIDI settings and choose the native resolution each time or should I set the MIDI to output 32/192 and just leave it?
Thank you.