Jag...trust your ears. If the sound via the 8ohm taps is fatiguing and you regularly end up turning down the volume to take the edge off the highs, you will end up listening a lot less to music which will be a shame. I suggest doing the following experiment. Hook up via the 8ohm taps for 1 week and keep a journal. Notice how often and how long you listen to music, if you choose only certain type of music, and if you end up cutting your listening sessions short. Most of all try to notice how much you are
thinking about the sound vs. how much you
lose yourself in the music and get emotionally swept away (the only real test of whether a system is doing it for you or not). And then switch over to the 4 ohm taps for a week and keep a journal and try to notice all the above again.
At the end of this experiment, sit back and read through your journal/notes and I am willing to bet that your notes will
likely point to the 4 ohm taps being the more enjoyable listening experience.
That is not to say that there couldn't be more optimal positioning that could ameliorate one aspect of the SQ or another, or that tweaking cables can help contour the sound to your liking etc...but my guess is this basic experiment will tell you at a basic level which taps serve up the music in a more pleasing manner and once that's decided you can go back to our affliction (audiophilia nervosa) and tweak away
