I still say dig through the archives for unreleased Quad.
Here's two other's that sprung to mind tonight:
The Guess Who - So Long, Bannatyne
The Guess Who - Live at the Paramount
Now, neither appeared in their entirety in Quad, but are basically the only two classic Guess Who albums not released. Bannatyne ranked MUCH higher on the charts than either Rockin', Artificial Paradise or even #10! But, we did get a few cuts from it on Best Of #2.
Same thing goes for Live at the Paramount. Would've made for an awesome 2-tape set if they'd have tried to put out the entire concert. (Hey, they did it for Elvis!) and again, we got one track from Live! on the Best Of #2.
Now, from what we've learned over the years with certain single tracks appearing on samplers, many times the entire album from whence those tracks came, were completely mixed and often finished - only left unreleased. This leads me to believe that at the very least, So Long, Bannatyne was mixed. Possibly Live!, but I doubt that one ever was. The only thing I think that would've killed Bannatyne was it's over 45-minute runtime.
Still, those would be two great Guess Who albums to put out. I don't think Live! has been re-released on CD in the last decade and I don't believe Bannatyne ever has. I would want to look for these to see if they were ever done. I want to hear Pain Train in Quad!!