Have been away for several days but get Trollheart's point here. I think the best idea would be to work through a general list (such as the one below, but it could easily be another list) This list for example includes around 217 album from really well known prog albums to some really lesser known stuff as well. This list could be randomized as well to make it less chronological as it runs from 1969 to 2013.
So therefore we would all be listening to the same album and could do an album a week or every fortnight, it's a huge list so it would take a long time to work through.
http://rateyourmusic.com/list/Mindcr...s_of_all_time/