First off, Cruising With Ruben and the Jets is about as progressive as Rocket to Russia.
Second, I'd add Days of Future Passed by the Moody Blues, Shine On Brightly by Procol Harum, A Salty Dog by Procol Harum, The Low Spark of High-Heeled Boys by Traffic, Traffic by Traffic, John Barleycorn by Traffic, On the Threshold of a Dream by the Moody Blues, El Dorado by ELO, ELO II by ELO, Hot Rats by Frank Zappa, Relayer by Yes, Ommadawn by Mike Oldfield, Absolutely Free by the Mothers of Invention, Aqualung by Jethro Tull, Mekanik Destruktiw Kommandoh by Magma, Pawn Hearts by Van der Graaf Generator, Lizard by King Crimson, 2112 by Rush, A Farewell to Kings by Rush, Hemispheres by Rush...hell, everything by Rush, Misplaced Childhood by Marillion (getting into the '80s...I'll save that for later).
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666 by Aphrodite's Child, Larks' Tongues in Aspic by King Crimson, Starless and Bible Black by King Crimson, Meddle by Pink Floyd, Wish You Were Here by Pink Floyd, Animals by Pink Floyd, Even in the Quietest Moments by Supertramp, Ashes are Burning by Renaissance, Octopus by Gentle Giant, Free Hand by Gentle Giant, In a Glass House by Gentle Giant, Three Friends by Gentle Giant, Godbluff by Van der Graaf Generator, H to He Who Am the Only One by Van der Graaf Generator, Script for a Jester's Tear by Marillion, Fugazi by Marillion, Lather by Frank Zappa (posthumous), Waka/Jawaka by Frank Zappa, Live at the Fillmore East by Frank Zappa, hell, everything by Frank Zappa, too; You by Gong, Camembert Electrique by Gong, Song for America by Kansas, Masque by Kansas, Leftoverture by Kansas, Phaedra by Tangerine Dream, In the Land of Grey and Pink by Caravan, Third by the Soft Machine, Fourth by the Soft Machine, Warrior On the Edge of Time by Hawkwind, Peter Gabriel by Peter Gabriel, Security by Peter Gabriel, Peter Gabriel III by Peter Gabriel, Per un Amico by PFM, L'isola di Niente by PFM, The Snow Goose by Camel, Mirage by Camel, Phallus Dei by Amon Duul II, Fear of a Blank Planet by Porcupine Tree, I Robot by the Alan Parsons Project, Lord of the Rings by Bo Hansson, and...that's all I can think of, at the moment. I'll be back with more later, probably.
Bridge Across Forever by Transatlantic, Images and Words by Dream Theater, Metropolis pt. 2: Scenes from a Memory by Dream Theater, The Inner Mounting Flame by the Mahavishnu Orchestra, Birds of Fire by the Mahavishnu Orchestra, Between Nothingness and Eternity by the Mahavishnu Orchestra, The Six Wives of Henry VIII by Rick Wakeman, Just a Collection of Antiques and Curios by the Strawbs, Grave New World by the Strawbs, Ghosts by the Strawbs...everything by the Strawbs, too; Hybris by Anglagard, Safe as Milk by Captain Beefheart, Mirror Man by Captain Beefheart, Ocean by Eloy, V by Spock's Beard, The Wake by IQ, Todd Rundgren's Utopia by Utopia, Voyage of the Acolyte by Steve Hackett, Focus III by Focus, Styx by Styx, Styx II by Styx, Equinox by Styx, (No Pussyfooting) by Fripp and Eno, De-Loused in the Comatorium by the Mars Volta, UK by UK, Nice by the Nice, Death Walks Behind You by Atomic Rooster, Roxy Music by Roxy Music, For Your Pleasure by Roxy Music, Stranded by Roxy Music, the Motion Picture by 10cc, Spirit by Spirit, AAAAND Spirit of Eden by Talk Talk.
That's it...for now.