I put the JJ 6v6's in tonight. . wow!!! They sound pretty darn good. They start cooking pretty heavily at about 12 o'clock (as opposed to 3 o'clock with the 6l6's). The volume is about 8dB quieter. With the combo of 6v6 and a HotPlate at -8dB, I get a really good tone at a reasonable volume. If I need it quieter, I can drop to -12dB or even -16dB, but there is definitely some tone sucking starting to occur at those levels.
At the end of the day, I'm at about the same volume for these two situations where the second case sounds much more like a cranked amp eq-wise:
1) 6l6 and hotplate at -16dB
2) 6v6 and hotplate at -8dB
In the end, I'm likely to run at -8dB or maybe -12dB on the hotplate with 6v6's. -8dB sounds perfect to my ears, but -12dB will probably make my ears happier in the long run.