New Svetlana Tubes

Has anyone tried the new Svetlana 6550c vacuum tubes such as being sold by Viva on Ebay?  Does anyone have anything to say about Viva Tubes?  It looks like Audio Research is now using EH 6550's.  Has any one compared these with the SED 6550c's?

I have purchased KT150’s - QUAD tubes from Viva Tubes recently. They shipped the tubes promptly, well packed and no issues with tubes so far.

You may find following guide useful,

I am going to be comparing stock EH 6550C with a pre production 2012 SED 6550C Svetlana "winged C" tube in next couple of weeks. 
I have purchased new tubes as well as NOS from Viva Tubes. No problems whatsoever! Always well packed, as described and delivered promptly.