You're probably right Adam on selling Quad by stealth. I had to specially order my SQ copy of "Wish You Were Here" from my local record shop just north of London) they had no Quad section for Rock/Pop. But when I went to Cardiff Uni in 1976, Spillers Records (the oldest reord shop in the world) had a Quad section, split in to the various formats. I used to look at the CD4s of the Doobie Bros & Joni Mitchell, but although I had a Shure CD4 capable cartridge I couldn't afford a decoder (I don't recall seeing a home build design in any of the electronic magazines at that time or I would have).
NB: Spillers Records was started in 1894 and is still going http://spillersrecords.co.uk/about_spillers/
NB: Spillers Records was started in 1894 and is still going http://spillersrecords.co.uk/about_spillers/