I have 7's and have tried several amps. To my ears and a consences of other valued ears, 7's sound best with tubes. With good ss, the 7's do come alive at higher volumes but they also lack mid volume level "presence." The tube warmth tends to bring out the mid volume sense of music. The ss has been several versions of ML and the tubes different Sonic Frontiers with some tube roling with the output tubes. Hope this helps.
Denny
Denny