tube upgrade for ar ls2mk2

does anyone know of a better tube for my ls2mk2 than the factory installed one? i have tube amps and tuner if this makes any difference. thanks
Try NOS Amperex Bugle boy and see if you like it.
I've been evaluting about a dozen of tubes in my ARC LS2B MkII for the past few months - Amperex bugle boy, world logo, D-frame, A-frame, 6922 PQ's, 7308s, Siemens 6DJ8, 6922s, Telefunken 6DJ8, Mullard 6DJ8, master series 6DJ8, etc. So far, the Amperex 7308 sounded the most neutral, accurate, focused and good soundstage in my system overall. The rest all have strong points in one of the areas, but lacking in some other areas. I thought the bugle boy was a bit bright and lean on my sytem. Mark Levinson + Sonic Frontier + Genesis + ARC + Thiels (all transparent, MIT cables + PS Audio PP300) But all of them have major improvements over the stock Russian tube. If price is a concern, the Amperex 6DJ8 world logo is a good alternative.