This is the first time that I have looked at this thread. Ron has done an encyclopedic job in explaining prog rock, especially to someone like me who knows just about nothing about the subject. This past year I have started engaging in some serious trading of tapes (15ips 2 track) with different collectors. Although my main interest is classical music, most of them have non-classical as their main interest, so I have acquired a large number of these genres of music, well over 100 reels.
From Ron's essays and other postings, I think these would qualify for the prog rock categories. The advantage to these are that they are 15ips 2 track copies of master tapes or copies of copies, done with high quality professional machines, about 4 to 6 generations closer to the master tape than a typical vinyl pressing.
Led Zeppelin - LZ1, LZ2, LZ3, LZ4, House of Holy, Physical Graffiti
Pink Floyd - The Wall, Momentary Lapse of Reason (in addition my safety master collection has DSOTM, Animals, WYWH, Meddle, Atom Heart Mother, The Wall Live in Berlin)
Roger Waters - Amused to Death
Renaissance - Novella, Scheherazade and Other Stories, Prologue, Ashes are Burning, Turn of the Cards, A Song for All Seasons
Genesis - Abacab, Genesis
Peter Gabriel - Shaking the Tree
Alan Parsons Project - Tales of Mystery and Imagination, Eye in the Sky, I Robot, Turn of a Friendly Card
Nick Drake - Five Leaves Later, Pink Moon
Steely Dan - Aja (in addition in my safety master collection Katy Lied)
Moody Blues - Days of Futures Passed, To Our Children's Children's Children, Seventh Sojourn
ELO - Messages
Yes - Fragile
I may have missed these artists in the thread - not sure whether they are prog rock.
Dire Straits - Dire Straits, Love Over Gold, Brothers in Arms, Communique, Making Movies, On Every Street
Fleetwood Mac - Mystery to Me (also have in my safety master collection - Fleetwood Mac, Rumours, Tusk)
Christine McVie - Christine Perfect
Stevie Nicks - ( in my safety master collection Bella Donna)
The Who (in my safety master collection - Tommy, Who's Next)
Now I have to start listening to most of these.
Larry