You aren't saying that "dramatic four-channel stereo" was a bit of marketing hype, are you?
Several years ago when eBay was new, I got into a knock-down drag-out scrap with another bidder for one of these Pioneer SQ decoders.
As luck would have it, I "lost" and it cost him a bundle. I eventually picked one up at a pawn shop for ten bucks, and found out what they were really like.
It is long gone now ... thanks once again to eBay ... wasn't eBay a great place before the scammers and "Super Sellers"? Sigh.