If I may "contribute" a couple of small corrections...
Both the Yamaha QX-1 and Korg SQD-1 came out in 1985, not 1986. I own a number of music magazines from the era and the ads and reviews on them are the source of that information.
You can see for example here (in the actual page scans) that as early as Feb 1985 the QX-1 was advertised as "coming soon" on E&MM:
http://www.muzines.co.uk/mags/emm/85/02/635And then in the Apr 1985 issue it's already on sale:
http://www.muzines.co.uk/mags/emm/85/04/637In the Aug 1985 issue (not online unfortunately), 'Dead or Alive' mention using it as their sequencer for their summer tour and there's more references in other issues/magazines
The Korg SQD-1 is reviewed in the Sep 1985 issue of E&MM and appears to be already on sale (i.e. not "coming soon") in ads within the same issue. My guess is they may have tried to push an "early release" before Christmas... The Korg DDD-1 drum machine on the other hand, which looks very similar in design, did in fact come out in 1986; maybe it just took a tad longer to implement the on-board sample technology and they couldn't be released at the same time.
Hope this helps!
