So, really, there isn't any point in sending the unit anything higher than 16/48.
Very informative. Thank you.
Actually there is, if the downsampling is actually done at the DAC level (on the output to the speakers). Then again, the Z-680s, though nice, aren't so high-end that you'll notice a difference. In any case, just set the sample rate to the highest possible, it sure can't hurt.