I'm retubing my 6505+ with some Winged "C" SED 6L6GC's. They're quite a bit more expensive than the JJ's, but from most of the reviews/demo's I've seen, they seem to go with the 6505 series really well. You can never go wrong with JJ's though :)
+1 to this and what Phil said about Eurotubes. I used tge SEDs with my Roadster and i may go back to them when my 6505+ needs new lightbulbs.