First post been a lurker for years. I just sold an slp 05 with the Upgrade after using it for about 5 years. Rolled many sets of tubes including NOS KenRad VT-163 and Marconi BL63 among others. Was always happy with the sound but I could never get rid of a slight crackle from the tweeter. It was always present, basically there was no dead silence when there should have been.
I believe it was the gain issue discussed but I could never defeat it.
Since my amp is an Arc ref75se I sold the Cary and decided to go the ARC route by purchasing a Ref6 a few months ago, I am never looking back as I am really enjoying the ARC build quality and sound. Considerably more money than the Cary though. Other than the slight hiss I still feel the slp 05 is a great piece of gear but I'm happy where I ended up.