To be fair I think I got a bargain on my BGRP. I don't actually know their current market value except Brent listed them at .... $525 per pair.
Do you think the RCA grey glass and Ken-rad are worth say ~$180 for each pair?
I think I'll need to research more on the Sylvanias - main problem is there seems to be a dozen of them. What are the good ones aside from the mega-expensive 6SN7W metal base? Any "preferred" era when they're made?