Law,
I think after reading the replies that there is strong evidence that speakers are your problem. Changing tubes, ICs or speaker wire will tweak the sound but not 'change' it. Stop spending money on tweaks and save for an 'upgrade.' To answer your question about Telefunken, I have found those tubes to be darker than others, but have a very sweet sound with good bass. A tube that would add a little brightness would be Siemens (as others have suggested) or an Amprex 7308 tube. But keep in mind, its a tweak, not a fix.
I think after reading the replies that there is strong evidence that speakers are your problem. Changing tubes, ICs or speaker wire will tweak the sound but not 'change' it. Stop spending money on tweaks and save for an 'upgrade.' To answer your question about Telefunken, I have found those tubes to be darker than others, but have a very sweet sound with good bass. A tube that would add a little brightness would be Siemens (as others have suggested) or an Amprex 7308 tube. But keep in mind, its a tweak, not a fix.