If you are on a budget and can't go to the Tung Sol KT-120 tubes I would say go for JJ KT88 Blue Glass tubes. In my experience with these tubes the sound and tone is clean but bass could be a bit thick. I've read that the JJ 6550 type tubes are just as clean sounding but the bass isn't as thick as the JJ KT88s.
One thing I find with the JJ KT88 tubes is that in my Jolida JD-502P it gets biased quickly upon turn on.
One thing I find with the JJ KT88 tubes is that in my Jolida JD-502P it gets biased quickly upon turn on.