4 or 8 ohm connection for a 6 ohm speaker?


I have a pair of Thiel CS2’s that have a nominal impedance of 6 ohms. My mono blocks have output impedance connections for 4, 8 or 16 ohm speakers. Is it best to connect the speakers to the 4 ohm or 8 ohm connections? 
Thanks for your thoughts.

Bill from Nova Scotia
wgs57
Hi jrwaudio! Well anytime you can get back to Nova Scotia it is even more beautiful...

The gentleman I purchased the two tube mono blocks from told me to always keep a speaker load on it when turned on so I was worried about trying a 6 ohm load on a 4 ohm tap initially but it all worked out in the end...4 ohm taps it is! Just being over cautious lol. 
I have lived all over the world . There is no place more beautiful than
Nova Scotia or better people than Canadians or a Country better than Canada .
Americans should thank God we have such a great neighbor we tend to ignore .
8 ohm has taps have worked much better for me than 4 ohm taps when driving 6 ohm speakers-  and it wasn't even close. 
but this is just a reference point- you really need to test carefully.   
Avanti1960, when you say I need to test carefully you are speaking of the sound quality? Would I do any damage to the output transformers by keeping a rated 6 ohm speaker load on 4 ohm outputs? 
I have settled on the 4 ohm taps as the sound is more complete at the low and softer in the high end. As long as no harm is done then the sound is great. 
Next change will be to upgrade the input or line stage I think it is called but that is for another thread :)

Best to you,

Bill
"keeping a load on" is in reference to never switching taps while the amp is on.
Enjoy :-)