Tom, FWIW I just finished playing with some EH's and Sovteks in my ARC SP10II as well as EH's and Sovteks in two different CDP's. Bottom line - IMHO of course - the Sovteks are more linear than the EH's but have no added warmth. The EH's can sound pretty good if you need some added sparkle and some more bass in an otherwise warmish system.
My re-introduction of my SP10II into my system caused me to change out the EH's from the Raysonic for a warmer tube, a Tesla 6922. And removal of Tesla's from a BAT DK5 and insertion of Sovteks as they were too warm. Two considerations must be made in valuing these comments. Both the ARC and the BAT use(d) Sovteks as OEM. The Raysonic used EH's.
Most folks don't care for the Sovteks that much, and if you don't need their 'ruggedness' as I do in my SP10, they will usually look for some good NOS Seimans or Tele's for clarity, linearity, and tone, or Amperex's if you want some warmth. But they are expensive and not easy to find.
Hope that helps a bit.
My re-introduction of my SP10II into my system caused me to change out the EH's from the Raysonic for a warmer tube, a Tesla 6922. And removal of Tesla's from a BAT DK5 and insertion of Sovteks as they were too warm. Two considerations must be made in valuing these comments. Both the ARC and the BAT use(d) Sovteks as OEM. The Raysonic used EH's.
Most folks don't care for the Sovteks that much, and if you don't need their 'ruggedness' as I do in my SP10, they will usually look for some good NOS Seimans or Tele's for clarity, linearity, and tone, or Amperex's if you want some warmth. But they are expensive and not easy to find.
Hope that helps a bit.