I realize not really anybody can comment on duelund in electronics.. I have no need for the Cast design as I have a feeling its just gonna be another level of diminishing returns especially in a 10 dollar horn... But worth it if you really want the best without replacing a speaker.
As for low frequency, Yes the 12 gauge copper ribbons from alpha core goertz are 10 times better, the power, low frequency response, balance and efficiency all seem increase substantially in all of the klipsch speakers I have upgraded in the past, ONE thing is to make sure however you can get the EXACT replacement value is purchased to replace the original, not one off the shelf that is just close.. I believe Goertz is in connecticut still and you can call they will sell you a pair of the exact value inductors you need.
However for the Horns I found that the Alpha core 14 gauge did not really mark a large improvement, you just don't need the energy for a parallel inductor in the horn circuit, I found a better sounding and easier to install inductor for the horn was a 14 gauge 800 watt Erse inductor, its an air core, not ribbon, which you can buy oversized and have a company wind it down for you to the correct value smaller, the ribbon inductors you can not wind down to a lower value, the erse also handles 150 watts more than the ALpha core, however of course 14 gauge and 800 watts is not even close to necessary for your 100 db horn, but I like overkill and good quality so I will only go down so far :-)
The erse inductors are about the same price as Alpha core of the equal gauge and value for your horn. But I still love the Ribbon 12 gauge copper on the woofers the best.