My dealer, who is also the local EAR service center, and a gentleman that mods the 834P, both highly recommend JJ88's. I think. I can double check if you're serious.
When I was considering purchasing the JJ's I found out that my EAR already had them ATOS. I was told that, around the time I purchased mine, that EAR had begun shipping units with the JJ's. But, mine were "short" or "medium" plate, and so still being curious, I purchased a set of "long" plate JJ's.
I don't remember noticing a huge difference, or even a medium difference in the sonic character between the JJ's -- the short or medium plate and the long plate. But, I kept them anyway sinhce it never hurts to have an extra set of tubes. And "long" plates are the ones that are currently in my 834P.