The difference between "good girls" and "bad girls" is that good girls choose who they're bad with......
On that note, I did in fact scrounge together a list of possible candidates. Some of which I'm not 100% on. This is just kind of a random musing from my end of things that might be worth checking into for any of you folks that may have multiple tubes laying around. I thought that it was said somewhere that mr. moffat was using the 6n1p and rather liked it. I think fox tried that and found it to run a bit hot. With that in mind I think the 6n6p probably draws over what would be comfortable with heater current but i had it on the list as a "maybe". Same goes for the 7au7, much in performance to the 12au7 but works off of 7v heaters....which a 6.3v heater is within the usual 10% figure I've seen thrown around.
Again, this is by NO MEANS a list of things you can do but there's a few of you here that are interested in rolling (and a few that are probably a slight bit more knowledgeable) and I wouldn't mind stirring up a bit on conversation on possible candidates.