Everyone's ears are different of course, but I'll be presumptious anyway and say that I think the DR's are the holy grail of signal tubes for the MW TP.
As for the Mullard GZ34, until you've heard a metal base, don't give up on that model. I realize they aren't cheap, nor available on every street corner, but WELL worth the effort. The difference between the regular black base and the metal, are night and day. Completely different sonic presentation. The former: syrupy, rolled at both extremes, wonderful midrange, good but not great soundstage and depth. The latter: fast, detailed, extended at both extremes, soundstage is wide and as deep as the ocean, depth is as it should be. It is one of those perfect combinations that allows instruments to float in their own little space, with perfect layering, and yet oodles of weight to every one of those instruments within that stage.
As I mentioned to ted in a PM, I'm done with my tube rolling.
YMMV 
Hey Case, your description of the Mullard GZ34 sound is exactly consistent with my own experience. Nice to see converging evidence.
I have pretty much settled on the 6H30-DR's myself as best signal tubes, but I'm still playing with a boat-load of 5U4 alternatives. My faves are still the Tung-Sols, especially the 5U4-G, but also the 5U4GB. The Sylvania 5931's are pretty good too, very different sound. I have been less thrilled with other Sylvanias, RCA's, GE's or Ratheon 5U4 types I've tried. I tried three types of GZ34's and all of them sounded like your description of the Mullards, to one degree or another. I had pretty much given up on the type, but your post suggests that might be premature. Thanks (I think). I'm too cheap to go for the metal base GZ34's altho I'll certainly keep my eyes open.
Oh, and thanks Dan for the caveat on the GZ32.
I used one for a month with no problems (a late Mullard), but I think I prefer the Tung-Sol 5U4-G, so I haven't yet gone back to it. Jury is still out, I haven't tried the GZ32 with the 6H30-DR's.
Fun stuff!
