Best sounding tube for ARC LS-2b

I would very much appreciate suggestions on replacing the stock tube in my LS-2b. Should I just order one from ARC or try something different?
Thanks, Geno
If you like warm, lust, mellow sound from your system. You should go for old tube likes Seimens or Philips. I'm using a ARC SP-11 MKII preamp, originally its used ARC sovtek 6922. Its sound very bad, likes solid state!!! I nearly sold it! But after I changed the tube to old Seimens or Philips. Wow!!! Major inprovement and I'm keeping the SP-11 for as long as I could(lust, warm and mellow and the dynamic is unbelievable)!! Forget about the sovtek, not even from ACR. I have some of the above tube just lying around. If you need any, let me know.
edle: just curious, what is "warm, lust, mellow sound"? i think i might like it, particularly with siemens. ;~)
we really like the Amperex tubes - if you can find some that were made for HP, wonderful. I have this magnifying glass program that you can load on your desk top and use when looking at pics of tubes on line - you can read date codes, etc. If interested, email me and I'll reply with program attached. could give you some information for going prices. you may want to see thread on "deals gone bad" to get some information on someone(private) that you don't want to deal with. good luck!