6550B tube recommendations for a AR VT-60

Hi folks:

I have an Audio Research VT-60 power amp. The 6550B bottles are getting a bit tired and I'm thinking about swapping them out. I've seen some ads for the "Flying C' tubes, as well as some others. I've had many tube preamps but very few tubed power amps so my personal experience in this area is somewhat limited.

I'd like some input on some decent replacement tubes for the VT-60 (or any similar AR amplifier) that won't cost me more than my 1st car did. Your experiences and opinions would be welcome.
I believe Audio Research uses SED 6550C's (Winged C's). They are highly regarded new production tubes. The are rugged and fairly balanced. Getting the tubes is easy, but are you up installing them. I'm not familar with the VT 60, but from my old D115 and general knowledge of a few other ARC amps, biasing in new tubes can be a PITA.
I have a ARC VT-60 and I bought the unit used with Sovtec
6550's already in place.The original owner stated they were brand new.The tubes put out a wonderful extended top end,and if a Walker SST is used or a similar product on the tube pins you will get a tighter,deeper bass response as well.