Capacitor

barely noticeable improvement, this crossover upgrade transformed the Moabs to a whole new level, night and day.

I was hoping the new Mundorf high priced caps would have transformed my Millennium tweets into something VERY XXP.
But sadly onlya  miniscule nunace = wasteful experiemnt, Now on the woofers, yes, there I got more than a  nunace. 
But sadly all the oney I put into new high tech xovers should have gone into my High sens driver purchase.
Now i am behind that budget some $1200++
Maybe you can tell your mids/highs are now more than a  nuance superior, while others listening o your new xovers may say 
*eh, well...i guess...*
To others thinking upgrading xovers is going to make your speakers into some all new, you are going down the wrong path,. Save your cash, go xover-less high sens.
based on a  painful experiement. 
Even Troels with all Z caps = xovers cost more than the drivers,,!!!!!...
Can not match a  high sens performance in mids/highs. 

$2k total cost of what I have

~~~~~~~~~~~~~~~~~~~

Thats about close to what I spent in the Mundorfs.
For $2k
you can get a pair of Neo High Sens AC1A’s from Voxativ.

Even Troels with all Z caps = xovers cost more than the drivers,,!!!!!...
Can not match a high sens performance in mids/highs.- mozartfan

How much to invest, and where the diminishing returns lay, is how well the drivers could possibly play together, how the cabinet works, and the crossover points implementation on the chosen drivers... - rixthetrick

@mozartfan - There's no surprise superior engineered drivers will produce a better result.

Yes, it is more complicated to know where and when to spend the money to get the best results for the investment. I am assuming you didn't just upgrade the capacitors and nothing else in the crossover networks? 

There's no blanket statement for crossover upgrades in the many varying speaker designs out there, on that we wholly agree.
Though, depending on the parts used, upgraded parts can be as results varying as using different ingredients in a recipe - substantial differences.

Indeed. One substantial difference, if the drivers are upgraded they will almost certainly be different response and therefore require at least some crossover changes. If the upgraded driver is a known commodity, like adding a Be tweeter to Moab for example, something the manufacturer actually does and knows how to do, that is one thing. But to just pick a superior driver that fits, well that is almost certainly going to call for a lot of crossover tweaking.

As opposed to not really changing anything in the design at all, but merely implementing it with superior quality parts. That is what I did.

Also keep in mind, not only the caps, resistors and inductors. Also the inductors are now oriented better, their axes all at 90 degrees to each other. Also they are mounted on Omega eMat. They are no longer mounted on a wafer thin bit of fiber board, they are now on massive dense carbon fiber BDR Shelf. They are no longer hot-glued to a brace, but isolated on Townshend Pods.

Each and every one of these changes would be a pretty decent improvement on their own. All of them combined is why this upgrade elevates these speakers to such a high level. The beauty of this approach is that by being so careful to use all the same electrical values this means all Eric’s original work is retained and nothing needs to be trimmed or adjusted or experimented with.

That's a big value and can get pricey, I've had good luck with Claity Cap CMR, Jantzen Aumin Z then for a smoother rich sound copper foil, Juniper, Miflex the copper foil are great for bypass also. Sonicaps aren't bad for the money certainly if you bypass them with a copper foil. If you have sand cast resistors pull all those out and add Mills or a little expensive the Path are nice. Re wire the cabinet can make a big difference. If changing out caps gets to expensive the little things like resisters, wire change, cabinet bracing does make a difference. Even with very expensive we'll know speaker company's once you open the speaker up you will be shocked the cheap crap they put in there.