So I recently splurged on an Amperex 7308 PQ (early large halo getter type, white lettering, Valvo branded, made in Holland, early 1960s) for my Project Ember. Although it hasn't been broken in yet, it is already a noticeable improvement over my Amperex 6DJ8 (white lettering, made in Holland for HP). There is a great deal more detail and soundstage is a bit larger. I'm noticing small nuances in the music that I couldn't hear with the 6DJ8. Imaging is crystal clear with the 7308 and everything is so defined throughout the entire sound spectrum. Noise floor has lowered to the point where it is basically inaudible unless you really try to hear for it when no music is playing. Vocals sound absolutely beautiful and everything just sounds so natural. I'm listening out of an AD2000X, with a Geek Out 450 as the DAC.