To get the knowledge base rolling, here are some resources that I have personally found worthwhile. Others can chime in and I will update this post.
Where Do I Start?
Previous Lyr Tube Rolling Thread: http://www.head-fi.org/t/549508/schiit-lyr-the-tube-rolling-thread
Joe's Tube Lore:http://www.audioasylum.com/audio/faq/joes-tubes.html#6DJ8
What is the consensus?
There is no consensus to rely upon really. Everyone has their own preference in terms of soundstage, brightness, etc. Further complicating the issue, different tubes may sound better with certain headphones.
Then what good is this thread?
If you have an idea of what you are looking for in sound reproduction, the reviews posted here can guide you toward certain tubes that are most likely to compliment your system at different budgets.
What are some of the more popular sub-$100 (per pair) tubes to consider?
'60s Amperex 6DJ8 "Orange Globes"
'70s Voskhod 6n23p "Rockets"
National Matsush!ta 6922/E88CC
6DJ8, 6922, ECC88, E88CC, 6BZ7, CV2492, CV2493, 6N1P, 6N23P
Edited by joydivisi0n - 7/24/13 at 7:56am