I've tried JJ ECC83S. It's well balanced and has good definition.
For the power tubes, there's the Sovtek 5881 (6L6WGC) and EH 6L6GC. The 5881 is darker sounding. It's supposedly military grade (from what I've read) and will last longer. I prefer the EHs, they sure sound sweet. It's brighter than the stock power tubes.
Oh, my amp hums like a bee, too. I wonder if that's the reason they call it ValBEE. Ha.hahaha... It's not very audible when playing but when I stop, I can hear it. With the boost engaged and gain turned up, it gets louder. Doesn't seem to be anything to do with the input. Is there anyone who I can send it to for a look?