Which McIntosh tap are you using with B&W speakers?

B&W' speakers are a nominal 8 ohm speaker but dip down to 3 ohms.  I am curious who uses the 8 ohm tap and who uses the 4 ohm tap on a McIntosh amp, and your thoughts on the differences.   It is also possible to use the 8 ohm and 4 ohm taps at the same time (mid/highs at 8 ohm and bass at 4 ohms).  Has anyone tried that configuration and how did that sound.  I have tried it all ways and I think I like the 4 ohm tap the best.  I will say using the 8 ohm and 4 ohm tap at the same time definitely gives a boost to the mids and highs over just using the 4 ohm tap.