I used many a tube variety in my previous LS15 and LS25. The ARC's sounded best with Siemens 7308 circa pre 1970. Then I tried some of the Cryo'd SLNM 6H23n-eb from ATSI. Ken Chait cryos these tubes and the results are nothing short of amazing. They have a sonic signature that resembles the Ediswan 6922 I tried and liked..but the Cryo'd 6H23n's are more transparent and more dynamic. Soundstage goes very deep which is something that none of my NOS tubes, Ediswans, Amperex PQ's, Siemens CCa's or Mullards could do. At $74.99 a pair..you should check them out. www.tubeman.com/item224.htm
Enjoy!
Enjoy!