Buy tubes from Audio Research or not

One more data point(FWIW):

I've re-tubed my VT130SE with ARC tubes and my Prima Luna 7 monos with KT88s, Kt66s, and EL34s from Upscale. Zero issues across the board. IME, both are excellent sources for re-tubing.

Marty

If you needed a catalytic converter on your 5 year old Porsche, would you get the parts from Porsche, or would you find the cheaper parts made for Porsche?

A catalytic converter is a catalytic converter. Either it works or it doesn't. However, that is for cars. For electronics, if one doesn't have the money, you do the best you can and take your chances. Just make sure the supplier has a good warranty or return policy. Audio Research supplying the tubes will warranty the tubes and if their tubes blow prematurely and damage their equipment, they will stand by their products and repair it for minimal costs or free. I purchased a set of tubes for my VTM 120 monos and my PH3 phono stage and one of the 6922s from the VTM blew and took out the fuse also. Well, I replaced the fuse and put an older 6922 in to see if the amp was okay. It was. But, I called Audio Research and told them about the failed tube and they mailed me a replacement. I don't know. dealing with companies that stand behind their products mean a lot to me and eliminates a lot of grief. But, it does depend on your price point. Audio Research supplied tubes are more expensive.

Enjoy

There are many tube companies out there like Newsensor. In fact that may be wear audio research is getting their tubes from. They own the Sovtek tube factory in Russia. No difference except Audio Research tests the tubes they get.

I just re-tubed my ARC D-70 Mk2 and I bought a matched quad set of winged C 6550's from Antique Electronic Supply. I also bought NOS GE 6FQ7's and JJ 6922 from them as well. I installed the tubes( probably easier to do than on a VT100mk111) and had my tech do the biasing. He discovered a bogus 6922 and so he replaced that at the time. ( I bought a couple of spare 6922's for this purpose)
I think the biggie with these amps is the biasing procedure, IMHO that is definitely NOT for the faint of heart.. ARC seems to think that the layman can do this procedure, to which I say they are NUTS!! Not only are you dealing with lethal voltages in the amp, but the various points to determine where to set the meter are not even marked, at least in my amp. ( and you need somespecial tools to do the job)
In regards to whether it is better to buy the tubes from ARC, i am of two minds on that... OTOH, I like to support ARC for their loyalty to their customers, OTOH, I think their pricing is not really reasonable and in my case
I wanted to tube roll, which they really don't do.
If you go with SED 6550's then I think that the odds are great that these tubes will work well in your amp and can be bought from any respectable supplier.