EL34 upgrade

The Winged C is a good choice and a definite upgrade from the three you've already tried. The Gold Lions are great tubes, but make sure they're compatible. KT-77's, KT-66's, and some 6CA7's are 7-pin tubes (originally 6CA7 was the American designation for the EL34, but a true separate tube was eventually developed as another beam tetrode). I really like the GL reissues, but I have one ST-70 that works fine with them and another modified one that's not compatible. Both the KT-77's and 66's are worth a shot.

The Shuguang Treasure 6CA7-Z's are even better, but they'll really set you back. I'm currently using these, and I even think they sound better than some of the NOS tubes I have or have used, but they'll pretty much set you back more than anything other than the really heavy hitter NOS tubes (Mullards, original Genalex, etc.).

I would strongly suggest NOS Siemens. Upscale Audio has them for $220 a quad, but you can find them for less. I actually have three quads of these that I'm not currently using if you'd like to try them.

Out of all the options and your stated price point, I'd suggest either the Gold Lions or the Siemens.

Good recommendations here. At the lower end of the price scale the SED Winged Cs are excellent. The Gold Lion KT77s I bought from Jim McShane were rock solid and sounded wonderful and I also really liked the NOS Siemens like the ones Upscale Audio is selling. The Siemens were made by RFT in East Germany and rebranded by Siemens but they're wonderful tubes.

Sfar is correct about the "Siemens" EL34's. Of the three sets I have, they're branded Siemens, RFT, and National, but they're all exactly the same. I definitely should have called them RFT's to be more accurate. Upscale does have the tubes branded Siemens, but these and most other German EL34's of this era (including Telefunken) were all made by RFT. Regardless of the branding, I do feel that they're excellent EL34's.

I would not avoid NOS Tesla's, they are very good sounding EL34.

I agree. The Winged C's are excellent for the price. I just got done recapping 2 Marantz 8B's and put 2) quads of the Chinese EL-34's in. Seem to be very very good and strapped the amps are putting out 77Wrms across 8 ohms. Can't beat that.