According to seafood watch, market squid are at the very least sustainable [0]. Squid and octopus are different I believe, but calamari is squid if I'm not mistaken.
As for Octopus, it appears a bit more iffy [1].
As for intelligence, that's secondary to sustainability for my eating habits at this point.
[0] - http://www.neaq.org/conservation_and_research/projects/fishe...