I can't say I've seen much of anything for the 8001, save for it being listed alongside the 9001 in a couple of catalogs. I figure they followed the same formula of offering a range of models that had worked so well in the past. The 8001 being the analog of an 8080, where the 9001 would have been the analog of the 9090. Really I think they could've skipped the 8001, offering just the 7001 and 9001, given the realities of the market at the time. The earlier quad gear (QS and QR models) received heavy promotion. The first lineup of QRX models as well. But owing to the time needed for development, by the time the 8001 and 9001 were available, the market for quad hardware was already in decline.
I am mostly speculating here, but I think Sansui realized that the market for quad was tanking right as their very best and most capable hardware came to market. This may very well have impacted the level of marketing that was done for the 8001 and 9001, as it would have been throwing good money after bad, so to speak.
The entire quad program was a gamble that failed to pay off, and I believe was a major reason for Sansui 's declining fortunes by the 80's. Enormous sums were spent on R&D, and marketing of the QS system and it's hardware, and while Sansui clearly sold a lot of it, it was a flash in the pan, public interest in it being mostly over and done by 1977. Hence the residual stock of 9001's still showing up in German print catalogs of 1982. I've no idea the price they were being offered at by then, but would be unsurprised to learn that they were sold at a steep loss.