Well if I would include Zappa - that wouldn't be fair. Ofcourse Zappa is as prog as it gets - but also undefinable in a genre - in fact plenty of his music isn't even rock.
Exellent list, I would add some Caravan, Camel, Gentle Giant, PFM, Soft machine.... aaargh it would take me some hours to make up a list and it would be quite a big list, I'm afraid. I already have problems making up my top 2013 albums list.
King Diamond - Omens