wife's observation

I have a Rotel RC-1070 pre and RB-1070 amp which power a pair of B&W804Ns. I recently replace my standard 14 ga speaker wire with 14 ga 4 wire (65 strands/wire OFC) and biwired the 804s. My lovely wife has commented that since the switch the sound level has dimished, meaning it is not as loud at the same volume setting as previously observed with the standard 2 wire speaker cable. Is this possible? i can't really tell a difference since we rarely go past 33% total volume. Thanks guys.

Since you went from single to bi-wire, the amp now has to work harder due to the extra cable. I guess it's the same priciple as shorter runs vs longer runs of cables.
Women in general are known to have a better high frequency hearing than men. Perhaps its just that your wife no longer hears high frequency aberations created by your original cables. She describes it as a lessening of volume when its just a lessening of irritating high frequency distortion or emphasis which makes the sound more pleasant and acceptible to her. Just a thought.....
Sounds like Newbee hit it right on the head. If you listen to a well balanced system, you can play it really loud and not notice it until you try to talk to the person next to you. Her percieved decrease in volume probably means your have brought your system to a new level.
Bigger is not necessarily better. All cables are filters that pass some frequencies better than others. The work of a cable designer is to uniformly extend the frequency and power output of the cable by altering resisitance, inductance and capacitance. The cable that you substituted probably has a lower resistance (bigger gauge size) but a higher capacitance (I cannot comment on inductance-not enough information given about the cable design). Your wife is hearing the change frequency and power output caused by the insertion of the new cable and the interaction of the cable with the speakers network.

By the way you should be able to hear this change too. It is not suttle.