6 ohm speakers with 4/8 ohm amplifier

Question: if my integrated amplifier has 4 and 8 ohm speaker connectors and my Harbeth's are rated 6 ohm - is it best to connect the Harbeth's to the 4 ohm connectors on my amplifier?
Whichever sounds best, don't worry, you won't hurt anything.
8 ohm may be fuller 4 ohm may be a little lean

try both it's fun!
I think the correct answer depends on the impedance curve of the speaker. 6 ohms is simply the nominal impedance. Without knowing the particulars of your speaker, I would say that the 4 ohm taps are the better choice, since the impedance will be lower than 8 ohms for much of the time.
As was said before, try both. It's possible you won't hear any difference. Only if the speaker's impedance drops into the 2 or 3 ohm range for a significant part of the audioband will the 4 ohm tap sound noticeably better.
For what it's worth I have revel performa30 with an arc vsi60 , base it tighter , Mids are cleaner on the 4 ohm tap. I wasn't happy with amp until I changed from 8 to 4 ohm
I have 6 ohm nominal KEF Q300 speakers and I use the 4 Ohm taps of my Jolida JD-502P amp. I found the bass to be slightly louder and tighter vs. the 8 ohm tap of the Jolida. I figure the KEF Q300s may dip below 6 Ohms so I might as well play it safe and use the 4 Ohm tap just in case.