I have tried a matched pair in my DAC and found that they made the system sound indistinct. For example, Miles Davis' trumpet on Miles and the Jazz Giants sounded tubby and a wall of hiss arose around the music. Gillian Welch's opening notes on her most recent CD sounded grainy. Christa Ludwig singing Mahler sounded hoarse. And so on. I gave them a week, then they went into a drawer where they've stayed ever since. Sylvania, GE and Raytheon 5750s have worked much better for me -- more clarity, no tubbiness, and more quiet. Maybe I latched onto a bad pair because there are people who like these tubes--who knows? But at their price, I'm not eager to experiment with a new set.
