Anyone compared 6922 Sovtek & Electro-Harmonix

I am presently using JJ E88C/6922's in my Audio Research preamp and find them to be very good. Of course my first choice would have been Amperex or Siemens, but I just couldn't afford to spend over $1,000 for 8 tubes.

http://thetubestore.com/teslaecc88.html