Hi calvin,
I am using a audioquest powercord of some type but I am not a great believer of them as I tried many different brands from my friends and never found significant improvement sonically unlike IC or speaker cables.
the tubes are using are sometimes mullard cv 4003 and rca cleartops.
tried this compares to your tube set up?
thinking of selling it due to the heat the S8 produces,just gets to hot in my room despite the fans blowing (I live in hawaii/rainy mountain side).
thierry.