How about an insane 10-tube all-tube headphone amp? It's something I'm playing around with. Of course, it would be about 10x the price of a Vali 2+. And it currently isn't ready for prime time (too much hummmmmmmmm...but fixable.) Still not sure I want to bring it to production.
Hard to improve Valhalla 2 without adding a bunch of cost. Or hybridizing. And then what's the point? It's supposed to be an affordable pure tube amp.
something along the lines of the ALO Audio Studio Six, at a relative more affordable price point ?
Studio Six: Amp: $4k. Nicer tubes: $1k.
Schiit Toastr: $600. Nicer tubes $4k.
Perfect for the serious Schiit head who has spent multiple-times the cost of their Vali/2/Valhalla/2/Lyr/3 on tubes.