My amp allows me to select either 4/6/8 ohm impedance with the turn of a dial. My other amps that have this either enable it by “under the hood” changes or different taps. When I first got it I went with 6 ohms as my Harbeth C7’s are listed as such. What is the impact of switching it—less from a sound perspective but I’d be interested in that context too—more from a tube life and driving my speakers perspective? On my last amp I went with 8 because it sounded good and changing it was a PITA so never thought of it again. If I play around and like the 4 or 8 ohm settting are there any implications I should be aware of? The dial lets me rotate it to make the change but does it take instant effect like changing the resistive load on an MC cart at the phono stage? Thanks for any context you can share.