4 ohm taps or 8 ohm taps?

You hear what you hear, if that's nuts then we're all looney. I would contact the speaker manufacturer on the second question, they can give you the correct answer. You will get some responses to your post here telling you it's okay and others telling you it's not okay and then it usually(not always) turns into a pissing contest between posters. Sad but true.

Actually, I think there is a better consensus (though far from a perfect consensus) on this question than on many other issues in audio. The consensus being to go with what sounds best. And no, you won't hurt anything either way.

Re question one, there are many reasons why it is possible, led by the fact that the speaker probably deviates considerably from 6 ohms at many frequencies. Also, the higher output impedance of the amplifier on the 8 ohm tap will accentuate the effects of the variations in the speaker's impedance vs. frequency curve, and will also result in a lower damping factor and therefore lessened bass control. Also, the plate circuits of the amplifier's output tubes will see differing load impedances depending on which taps the speakers are connected to, with resultant effects that will vary depending on the amplifier design.

The bottom line is that the amplifier-speaker interface is complex, and both components differ from idealized models in many ways, meaning that the only way to reliably predict what is best for specific components is to listen, and perhaps to compare notes with others who have used the same or similar components.

Regards,
-- Al

I found an interesting forum response at this url......http://en.allexperts.com/q/Audio-Systems-835/matching-amp-speaker-impedence-1.htm