I was involved with David Powers in the Vision Acoustics project in the early 1990s. We sold a total of about 80 pairs and received a very positive review from Neil Gader in the Absolute Sound, Issue 91 on page 127.
The cabinets were sourced from a cabinet shop in Benicia, California which also made the NHT cabinets at the time. The 8 inch woofers were SEAS or Scanspeak (can't remember now) and the mysterious tweeter under the dustcap in the center of the woofer was a piezoelectric from Motorola. David designed the crossovers himself and voiced the design using Roger Modjeski's RM-5 preamp and RM-9 amplifier so, yes, they worked well with tubes. As they were sealed cabinets, you needed some power. At that time the SET movement was just getting underway. I was contacted by Harvey Rosenberg, Herb Reichert and Don Garber about mating their amps with our speakers but a few watts was not enough unfortunately.
We had our run but ultimately split up and I know David came up with a very sophisticated looking cabinet and a new partner soon afterward. I don't know much about his success beyond that point. I do believe he is still in the Denver area.
As for speakers, placing a "wanted" ad might be your best bet. I no longer have any.