Xover parts quality,/sound difference?

Sure quality parts can be important but the total design is what matters.I do tend to use simple semi 1st order networks with very hi-quality parts in many of my loudspeaker designs also very hi-quality transducers and cabinets.Then like Bobby said its very easy to tell the good from the ugly.In more simple designs with highly complicated crossovers I can skimp on parts costs a bit without much penalty soundwise.

There are also many spots in a crossover that make little difference if you use cheap parts or not. Wasting all your money on exotic caps in a low pass circuit usually makes no sense unless there is a specific design need for it. I will agree that higher end components often sound much better in the mids and highs, but only when properly implemented. A badly designed XO is still bad even with high end parts. In addition, things like silver ribbon inductors etc are extremely expensive, and putting these with a $20 tweeter will not get you a good sounding speaker. There are bargain drivers that sound very good, and some speaker manufacturers are notorious for filling a fancy box with $20 drivers and charging $10,000...however many other incredible sounding speakers use very expensive drivers ranging from ribbon tweeters to ceramic and beryllium mids, so to say these benefit 97% from the crossover is misleading to say the least.

After over twenty years of building and modifying speakers crossover design and components remains a bit of a mystery.
I really think that most good speakers are just a fluke synergy between crossovers components and drivers and something that is hard to replicate in a different set of components.
Of course a lot of experimenting and listening must help but this does not explain why companies with huge research and design resources [Focal,Jamo,Mission,B&W etc]fail to achieve consistently good sounding speakers.Some models are good,others are not,and yet each speaker probably has similar development input.This is also why many cheaper speakers,with cheaper components,often sound better than very expensive ones.
Companies like Spendor and Proac which are highly regarded for the consistency of their speakers and driver integration tend to be very conservative in their model changes and drivers used-as if they evolve new products from long running successful designs rather than designing them from scratch.

Sbrtoy, I agree, low pass can definatley work well and even better with standard 1 dollar to 15 dollar caps eg. Solen, Auricap etc...

My statements were made to be VERY general, as to simply say yes better parts can produce far better results, and then I used some simple examples just to give what flavors can change, that is all..

But none of this stuff is provable until the hardcore audiophile trys it, and believe me there are much worse mistakes and costs that audiophiles make then maybe taking a 5000.00 pair of speakers and having the guts to get in there and throw in some equal value higher quality parts. And Nobody said 97% is the crossover, Actually I said 90% of the Final sound in the product will be based on how well the crossover is designed, implemented, Executed, and has definate lean against the quality of parts.

It was not so spelled out maybe, but that is what I meant if this is what you are refering too. So sorry to mislead.

I have upgraded the caps, resistors and air core inductors on all three pairs of my Klipsch speakers and can tell you for a fact that I HEARD a tremendous difference in sound. I replaced the stock caps with Kimber Kaps, stock resistors with Mills non-inductive resistors, and stock air core inductors with Madisound.

I lived with all these speakers stock for about 5 years, so I was very familiar with the sound. What I heard after I upgraded the crossovers was nothing short of amazing. Trust me, I wasn't TRYING to hear something either to justofy the less than $100 in parts cost.

Bottom line: better parts do make a difference.