If you've tried the GL KT-88's, and want a change, you may want to try the GL KT-66 or the KT-77. I have a quad of the KT-66, and I do think they're closer to the "euphonic" midrange. They aren't compatible with my main setup, but they sound great in my original circuit ST-70 (though I do have to mess with the bias). I would probably give them a chance if I were you.
Upscale Audio still has a bunch of NOS Siemens EL34's in stock if you just want to try those. As far as I've found, the closest current production tube to the original Mullards is the winged C ( =C= ). It's the same tooling/design/factory as my NOS (pre-Sensor) Svetlana's. They're usually price around $150 for a quad.
Upscale Audio still has a bunch of NOS Siemens EL34's in stock if you just want to try those. As far as I've found, the closest current production tube to the original Mullards is the winged C ( =C= ). It's the same tooling/design/factory as my NOS (pre-Sensor) Svetlana's. They're usually price around $150 for a quad.