Cary SLP-03 Tube Preamp- Ultimate Upgrade

Interested in finding out more about the ultimate upgrade available (for the SLP-03) through Cary Audio for this preamp. The factory confirms that this can be done and I wanted to know if anyone out there has had it done, if so was it worthwhile and what were/are the benefits over stock unit?

Unfortunately I cannot comment on the SLP-03 but I did have the ultimate upgrade done for my SLP-05 and thought it was more than worth the money. Not only did it sound better but they checked everything out and replaced a couple parts that weren’t up to spec.