My upgraded PH-9X arrived in Denmark a few weeks ago, and it has now had about 50 hours of use. I originally ordered the version with balanced out, but found that it sounded best single ended.
The upgrade is imo definitely worth the expense. It has transformed a great phonostage into a magnificent one. All it's original virtues are intact, but the insight into the music has expanded considerably due to it performing at a much higher level. I am now running balanced out with my favorite Amperex USN-CEP 7308's doing it's magic.
It is difficult to describe the update in audiophile terms, so let me try by giving score:
If the PH-9 has a score of 100 in it's original form, then the PH-9X would get a conservative 150 score in my book. That is quite a lot, as we are already up in the higher levels, where differences are small.
It is hard for me to believe it can get better than this after the transformers has had more playing time, but I will gladly accept it.
All in all: If you upgrade, prepare yourself for quite a sonic revelation. I am extremely satisfied.
Best Wishes from Denmark