Some more try-outs.
I tried some raytheon triple mica 7044 and rca triple mica 7044. These are also excellent, great drive, body and clarity. I would call these "siemens-like", and seem to show off the Steelhead best as a "sound microscope" but with reasonable warmth. They seem to have the biggest soundstage and the most immediate imaging.
GE five star 5687 are the smoothest and warmest sounding. A little less drive and punch, but possibly ideal for solid state amps. I did not prefer them to the Tung Sol 5687 or the Raytheon/RCA triple mica 7044 in my system.
I still prefer the Tung Sol 5687 overall in my system. They don't deliver the extreme clarity of the raytheons/RCAs, but they have a response characteristic that I crave in tubed sound. They are punchy and sumptuous. Silky highs cascading down into a limpid pool of midrange and bass transitions.
The only other tubes that might be useful to try in the 7044 slots would probably be the Bendix 6900 (expensive and overkill?) or the Amperex 7119 ( too much mu compared to transconductance?) but I am satisfied with the great improved sound from these other inexpensive tubes, so somebody else can try those.
Just as a caveat, I have the Steelhead hooked up as a line stage now feeding a tubed vintage Luxman crossover feeding VTL 450 sig's in triode to the MRT of Apogee speakers and Bel Canto 2002's to the Low Panel of the Apogees. The crossover uses the somewhat cool sounding telefunken 12au7's, which might be the final arbiter of sound before the amplification stage.
However, when I hook up the Yamaha RX-Z9 with it's solid state amplification and using passive crossovers to the Apogee's, the sound dries out a little but the general impressions remain quite similar.
I also tried putting Ediswan CV2492's back into the 6922 slot in place of the orange globe amperex 6dj8. I would just call that a different variation of wonderful sound, the Ediswan having the edge in body and balance, the amperex the edge in warmth and sweetness.