Hi, I had the Unico SE Amp two years ago that had 2 Electro Harmonix 12AU7/ECC82, but EH doesn't offer tubes labelled 5814a so they could be CBS or Sylvania or ... (you'll have to take off the lid after all I suppose)
Anyway, I substituted NOS Tesla ECC802S (not JJ!) for the EH which was a remarkable improvement to my ears. Good 12AU7 NOS tubes appear to be still affordable compared to a number of other types so there is some room for experiment. Here are a few pages with a short description of the different 12AU7 varieties:
http://www.machmat.com/sales/ecc82.htm
http://www.jacmusic.com/nos/ECC82.htm
Good luck
Anyway, I substituted NOS Tesla ECC802S (not JJ!) for the EH which was a remarkable improvement to my ears. Good 12AU7 NOS tubes appear to be still affordable compared to a number of other types so there is some room for experiment. Here are a few pages with a short description of the different 12AU7 varieties:
http://www.machmat.com/sales/ecc82.htm
http://www.jacmusic.com/nos/ECC82.htm
Good luck