I rolled a couple of NOS t7s, and liked the Telefunken ECC801S best. The other t7 were 6201 RCA blackplates, which were nice but not as detailed or extended as the Teles. I also tried a pair of u7s, RCA cleartops w/gray plates, and they were airy and sweet but didn't have the soundstage or presence of the more powerful t7s. The volume control with u7s was much more controllable though. The stock tubes that came with the 150 had no lables, but Paul tells me that they're "a Chinese Mullard double mylar knock-off T7's." I think we can all agree that the stock tubes are nice, but quality NOS tubes really take it up a few notches. The change is very noticeable, and my cds/mp3s have new life. In fact, I've stopped my hunt for a tube cdplayer - for now. Btw, my amp is Paul's TAD-60. I also rolled the pre tubes there and the difference is just as great as rolling the powertubes. I settled on a x7 Mullard short plate, but want to try a long plate and Bugleboy next. Also, I responded last night, but for some reason it didn't post, so my apologies if posts twice.