Three compilations; Utopia — The Collection, The Very Best of the Doors and Best of Alan Parsons Project.
Unfortunately, this collection concentrates more on the later power pop/new wave than progressive side of Utopia. Still, it has a few of fairly rare examples of 1970s US prog. Todd Rundgren's solo album Initiation (1975) was very proggy too, so Todd was really embracing the genre around the mid-1970s.
There are some pretty good poppier songs too
I've never been crazy about the Doors but I began to feel ashamed not having any of their albums. I like these so called deep cuts
Yes, "Sirius" is overplayed nowadays, but I've always thought that it and "Eye in the Sky" is one of the best one-two punches on an album ever (wisely, it opens this compilation too)