My original reco was just to help you identify the tubes that you have. I see that everyone else is chiming in with their personal favorite NOS tubes. I have heard them all, Siemens, Telefunkens, Amperex, Mullard, etc. To be honest, they all have their strengths and weakness'. All are much better sounding than current stock Russian/Chinese tubes.
I would say that the Mullard's are the warmest, if that's what you seek. The Telefunken's are also warm, but with a tad more air than the Mullard's. The Amperex and Siemen's offer even more extension in the high's, but are not quite as warm (sweet). Currently I am using Telefunken's in my VAC line stage (and phono stage) and I am quite happy with the sound.
Cheers,
John
PS: according to the VAC manual the four tubes are (2) 12AX7's and (2) 12AU7's.
