If it's too good to be true, it usually is. That said, I've contacted M in the UK a number of times, specifically Dave Hall, and he always gave me full details of previous owners, confirmation of speaker, etc within a couple of days. Now that Dave is working in R&D, not sure who would be the best contact. I think in this case, you're right and it wouldn't have made any difference - scam!!

3x DSP5200 L, R and C (all vertical), 4x Triad Silver in-wall surrounds and 6x Triad Silver in-ceiling ATMOS speakers, Triad Silver subwoofer, Denon AVR-X8500H, JVC DLA-7500 4K projector and Screen Research 120" AT 2.35:1 screen.
Apple TV 4K and Oppo UDP-203 Blu-ray player.