Resistors

aural acuity is not the issue. The issue is lack of evidence. If you were blindfolded, could you identify which resistor was which 100% of the time? 

I find the Duelund’s very very curious. They are deliberately temperature sensitive, which in the right place in the crossover could compensate somewhat for thermal compression in the driver. In the wrong place it could go the other way, and what happens if you don't have compression in the driver? This type of behavior is usually what we like to engineer out of our crossover.

I prefer to usue Mills for accuracy, thermal invariance, sound quality and small size for the wattage. They’ve always been glass smooth to my ears and good enough better compared to sand cast that I’ve not looked further.

I upgraded one channel at a time, from OEM sandcasts to Mills MRAs, and  compared them side-by-side using a mono mixdown. Obvious difference between them.

IF you feed the Troll, resistance is futile

So the way I found out about this, drove down to Oregon where my speaker's designer demo'd his new tweeter for me. It sounded great so I bought it. He said it requires a different crossover, which he showed me, and satisfied I could build it sent me home with the simple circuit diagram.
I went down to Radio Shack, bought the parts, put it all together, and called him up. This thing sounds nothing like what I heard at your place! It frankly sounds like crap! And no not "warm it up break it in" crap but "pure unadulterated never gonna get better crap." He asked me a few questions one of which was what parts did you use?

This was all years ago. Very hard to believe at this stage of my development. But, he must be right. I mean, everything else was the same. What else could it be? 

Week or so later after swapping in the much more expensive parts wow, world of difference! Now sounds just like what I remembered hearing at his place.
What this proves:1. Auditory memory is a lot longer than some people think; and
2. Parts quality makes a lot more difference than some would have you believe.