The Sylvania had a touch more "air", Otherwise identical performance. Nice! The 6L6 should give great Soundstage and the 12ax7 should give you very lively performance to offset the 6L6 distant. I can see that as a nice combination. So just depending on your dac aggressiveness, it probability sounds sweet for you... The advantage of this amp is the ability to fine tune and match with any gear thru such a wide range of tubes... It's all about the synergy of your system. That's why tube Amps have advantage to "tune", and especially this one! The list in this thread of tubes tried is already so much already. Since I have yggy as dac I went for most clarity in tube Choice, and the latest choices work nice. I would suggest everyone try the 14AF7 type(&14F7), and feel the metal base is better quality than most.