I believe the "best" tube for your preamp is dependent on what you and/or your system needs. I used to have a highly modified DAC with a tube output stage, both tubes protruded out of the top cover so they could be rolled in 15 seconds. I must have rolled those tubes 1000 times. I finally had one Amperex Bugle Boy and one NOS Mullard in there. Each channel ran though 1/2 of each tube so I got a mix of both tubes. If needs taming down there is nothing better than a NOS Telefunken smooth plate, smooth city. Good luck.