Buy tubes from Audio Research or not

Buy from the open market, but from reputable, well-established tube vendors. Flea-bay is a real crapshoot w at least a 50% not as advertised rate, IME.

Check out TUBEDEPOT SED SV6550C. Just order matched quads or better yet 8 matched tubes!!

it is sort of like the way my dad likes to buy cars from his local franchised car dealer. he ends up paying more, but to him it is worth the peace of mind.

with your amp-ARC uses the sames tubes available around the internet, but for the price you pay, they are hand-selected by them and fall within the parameters suited for your amp-----you may end up at the same end result with an aftermarket source, but there is always the chance you may end up with some issues.

Taters if you're worried talk to Howard at Audio Specialists in Studio City he's a great tech, repairs ARC and will know what does and doesn't causes problems.

Do more research. I could be wrong, but I remember there being problems with retubing and biasing VT-100 amps. Unfortunately, I don't remember which version of the amp. What I do remember of the discussion was that Upscale Audio would no longer sell tubes for the amp because of the problems buyers faced installing them.