Best modern 6550 tube for ARC per-amp

That's another thing I like about JJ, besides the sound quality, which is very near the top, you get a price that is very near the bottom.   
Almost all Tubestore.com tubes come with a 90 day warranty. The warranty on their Preferred Series is 6 months. I have never in nearly 30 years had a tube fail between 90 days and a year. In fact, I don't ever recall a tube failing in under 2 years, except for a couple Preferred Series tubes that blew within one month! The only tubes I would strongly advise against, had the best warranty. The extra you pay would seem to be for the warranty you will use. Hard to imagine anyone seeing the way mine failed would consider that worth the risk.   

All the many others, if they make it past the standard 90 they probably will go a good long time. Paying extra for a one year warranty in other words is a good profit center.

Brother. Just so you know, by this "logic" the diodes, power supply caps, fuses, transformer, power cord, AC power conditioner- none of that matters because "it does not directly participate in the amplification circuit of the audio signal". The reason they call it "parroting", the bird too is just repeating sounds it knows not the meaning of. And yet, at least it doesn't get too snooty about it. Score one for the bird.

Meanwhile, back in the real world (or at least planet WeCanHear) where tubes do make a difference we can hear: JJ. These are the tubes you are looking for.