Rookie Question, maybe

I have finally brought home the Primaluna Prologue and LOVE it.  Here is my question.  I have a set of Martin Logan Bookshelf speakers that I am using temporarily until the room that the amp and speakers are going in is finiahed.  The speakers are rated at 4ohms but compatible with 4,6, and 8ohm amps.  The Primaluna have speaker hook ups for both 4 and 8 ohm speakers.  How should I hook up the speakers to get the best sound but not overload the amp, or does it really matter?  I listen, for the time being, at low to medium volume.

I'm of the mind you should try all options and different ohm selections ,then pick the one that sounds the best ,there are no mandatory settings with that speaker .
I don't use the 4 or 8 ohm rating of the speaker to decide which tap to use. As a starting point, I check the impedance curve to see how demanding the load is. But that information isn't definitive.
In the end I find that listening to both taps will determine which sounds best.
I’ve been playing around with the different outputs and come to the conclusion the it almost sounds like the speakers are working harder when hooked up to the 4ohm output.  8ohms it is until I decide that it isn’t.  Thanks for the tips!