Bowie's cool in my book.
I've found some nice tubes in old army surplus gear. (I went tube mad a year ago - abstaining now
they weren't cheap. everyone knows what's good. well mostly anyone
though... you can try. also check out rebadged tubes, AEG, some consumer audio brands
I'm using these in an SPL Kultube (tube amp output stage) and SPL Charisma (tube effects amp, not the best design ever but I like it a lot)
the differences between characters of different tubes are inmediate and very noticable in both these designs.
RCA (blackplate) not a bad tube, not a bad price
Philips (Miniwatt, Eindhoven prod, or Mullard) rock n roll these. less defined, less beautiful than Tele's
Some Tesla early production (be careful there are fakes around)
Telefunken already mentioned (look for the diamond in the glass bottom (Raute)
Mullard (Blackburn) already mentioned
RFT - east german made. have a good pair - rock n roll but no Telefunken
JAN if you want clean modern and sterile compared to the older stuff (but good quality - double mica Philips made often)
Siemens - not as euphoric as the Tele's but there's some good ones
Sovtek - they were stock in my SPL gear, and break up in a muffled rock n roll way, they do have character, just not as open and strong sounding as the tele's or Philips
JJ - chinese made. got no experience.
hope this helps.