I'm not sure what it could be categorized as, but as far as the most amazing '70-'76 psych-sci-fi-cosmic-space-proto-punk-fantasy-cosmic-rock, Hawkwind has to take the crown.
Maybe but they were a British band so don't really qualify as Krautrock.
Here's a few Krautrock albums I would add to the list:
Can - Monster Movie
, Future Days
Agitation Free - Malesch
. I'd start with 2nd which I think is by far their best album.
Cluster - Zuckerzeit
Ash Ra Tempel - New Age of earth
, Inventions for electric Guitar
. I never got into their earlier stuff, these two are considered transitional albums as they moved from the more pure freakout rock to more cosmic electronic sounds similar to Tangerine Dream and Klaus Schulze.
On a releated note some of Edgar Froese's early solo albums are worth a listen, Mainly Macular Transfer
, and my all time favorite Epsilon in Malaysian Pale
. Their are tons more, I would have to dig through my collection for some more, maybe later.