What would you upgrade next if you had my hifi ?

Not sure what you are doing about power, but in my experience getting a PS audio regenerator (first powerplant premier than upgraded to P5) was a huge boost.

Second, I used to have Studios as well. Then I did an in room shootout with Verity Audio Parsifals and decided to keep the Parsifals. I then did the same between Parsifals and Eidolon visions and prefered the Eidolon's. I now feel I am a few steps up with the Eidolons from where I was with my Studios. Lot more $$$ though. For current used price the Studios are hard to beat.

And it brought the looks into the 22nd century. I always loved the aestetics of the original Revels.