Sovtek 6550 - Can they really be THIS bad???

Hello.

Just picked up a new Jadis today, and I'm none too pleased with the sound. As I have had blissful sonic experiences with two of the models lower on the Totem Pole from this manufacturer, the only thing I can trace it to is the Sovtek 6550. Can they really be THIS bad???

I already switched out the JAN Philips 12AX7 and Golden Dragon 12AU7 for Mullard Blackburn and Ei respectively. The improvement has been subtle, but it still ain't working for me...

I have used ElectroHarmonix 6550 in the past, and while they didn't float my boat, I'm told that EH represents a signficant step up from the regular old Sovteks. JJ E34L and KT88 just have sounded really splendid to me. So, now I'm looking at picking up 8 new output tubes if I don't wish to live with such uninspired sound.