Seems like there is controversy re: 7868 tubes nos & EH 7868's . Some say the nos sound better? I'm in the process of likely replacing all tubes in the Bogen, except the 12ax7. It takes a 6c4,6eu7, 12ax7, & two 7868's, screams like a banshee ( in a good way) but rumbling on low notes. I don't...