Brian,
Not necessarily, just that running a speaker with a lower impedance than the tap generally results in a bit more power, but at the cost of more distortion, and that's usually experienced in the bass, though it sounds like at the levels you listen, it may not be an issue, especially if you are running 2a3s in the 45 configuration on harbeths.
Of course the opposite is also true, that running them on the 8 ohm tap would be slightly less power, but less distortion, and for the same reasoning above, maybe that would work better for you.
Without being there to hear the setup, as I said, it's difficult to make a real recommendation.
-- Jim
Jim Rebman -- recovering audiophile
Equitech balanced power; uRendu, USB processor -> Musette DAC -> 5670 tube buffer -> Finale Audio F138 FFX -> Cain and Cain Abbys near-field).
s.e.x. 2.1 under construction. Want list: Stereomour II
All ICs homemade (speaker and power next)
