Tubing an Audio Research VT200?

I have been told by a well respected repair/upgrade expert that the 6922 tubes in this amp are selected by ARC for higher current capability and are very critical to the amps performance and the ability to safely bias the amp at the rated levels. I've also read on Audiogon that some tube rollers have ended up with serious damage after replacing driver tubes. My personal experience with Sovtek 6922s is that there are many options that will improve the performance. I believe there are 10 6922s and 8 pairs of matched 6550C Sovtek tubes installed. Any suggestions?
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Check out http://mycollins.net/audio/artube1.html good instructions for the VT-100, shows test points & adjustment pots to balance input tubes. If not using ARC sourced 6922's you may need several extra 6922's to get everything in balanced. A maddening experience as adjusting trimpots affects the other trimpot on that channel & you must get them to match. ARC can also fax you an instruction sheet with that may have different voltages & trimpots in the vt-200
I would definately call ARC and talk to them about it.
Unless Sovtek is amking them custom tubes I find it unlikely a Sovtek 6550C is any different in it's current rating.
I know though ARC gear is not easy to retube and bias properly. Suggest getting ARC or a well qualified tecnician to do it properly to assure long life of everything concerned.