Hi Mike.
I had X-model crossovers installed in my pre-X Khorus last year. I personally drove the speakers to the Talon factory in Utah. When I arrived, the folks there dropped everything they were doing to work on my speakers. I also got to meet Talon founder Mike Farnsworth who gave me a tour of the factory. Overall, I was very impressed by Talon's first class service and commitment to its customer. As for how the X-upgrade performs, after getting my speakers back home and playing them for a while, I noticed a bit more top end extension and slightly tighter image focus (the latter may have been due in part to a relocation of my speakers from their pre-upgrade placement). On the other end, I can't say I noticed a significant increase in bottom end extension after the upgrade. However, in my modest sized listening room, the pre-upgrade Khorus already went down to the limits of my hearing, so the X-upgrade could have extended the bottom even more and I just wasn't able to hear it. Also, I changed amp and cables within 60 hours of getting the X-upgrade, so there may have been other improvements in the speakers' performance as the crossovers got run-in that got masked by these concomitant component changes. I'm currently driving my Khorus with an Aloia PST-11.01 and ST-13.01 and AudioTekne cables. Very satisfying with remarkable clarity and evenness across the spectrum. (In an older thread, I believe you were the first to recommend this set-up, so thanks for the sound advice). If you get the X-upgrade done to your Khorus, I'd be interested in hearing about your impressions. Don