Liquid Sky is the ultimate punk/new wave psychedelic surreal SF movie from the '70s. Given your list, you should definitely watch that.
Also,
Brazil, though much less obscure due to the Monty Python connection, pure genius.
If you really want "surreal science fiction", you might want to give
Alphaville by Goddard a try. Be prepared for it to be frustratingly French, but it does fit that bill perfectly.
Eternal Sunshine of the Spotless Mind is surprisingly along the lines of A Scanner Darkly thematically. Jim Carey was surprisingly likeable and engaging in it (usually he's a funny asshole, here he's much more human).
Videodrome is a classic of the genre you seek, if a tad dated (betamax tapes and all.) Still quite good in it's own right.
Aeon Flux was way better than I would have guessed it would be, and the original cartoons are worth renting too. Charlize Theron looked damn good in the costume as well.
Soylent Green is another classic, though you may have seen it. If not, it should be up on your list. Weird how Charlton Heston was in this and
Planet of the Apes which are seemingly such liberal political agenda films, while he is such a loonie right winger.
The Quiet Earth is a nice little post-holocaustish surreal SF flick from Australia.
The Man Who Fell to Earth is one of my favorite movies period. Nicholas Roeg's direction of Bowie creates the most realistic feeling alien on Earth movie ever.
All I can do for now, I've got to run to work. Worth digging around a bit
here too, though admitedly the
SF message board I help admin is better with books than movies.