I have owned a JP-200 since 1993. During that time I have had it modified, and then restored to factory specs. I have used Telefunken, Ei, RCA, GE, Tesla, and Electro-Harmonic gold-pin 12ax7 tubes and have always returned to the Telefunkens. I have achieved a brighter sound but never any sparkle unless the Telefunkens are in the system. The Ei tubes were my second choice.
During the modified period, there was greater top-end sparkle; however, the unit also lost all of the musical characteristics for which one selects a Jadis product! To be clear, I do not recommend this option.
An idea, audition Mapleshade planar power cords (the active version with battery box) on the JP-200 or, on your power amps. This will change the balance somewhat, but not the character of the Jadis -they do open up the top end in a rather natural way.
By the way, what is the production year of the unit? I ask because this advice may not be as applicable to more recent production units --later than 2001.