I have read several threads here on the Zed regarding 572B's--and the final analysis is clear as mud. Some like Svetlana's, some generic Chinese tubes, etcetera. Ultimately, I find that the selection has boiled down to NOS American made tubes, or the Chinese variety. I understand that the Taylor tube sold by RF Parts is a Chinese tube--but ultimately how well does it hold up? Especially for horizontal mounting (SB-200)--and how do these compare to the Chinese tubes sold on ePay that have the circle and bird logo?