Yes, adult swim is my choice as well.
As for fox, i would say no, for one, fox doesnt have any programming like a dark comedy animated series, and it just wouldnt fit, if im making sense.
As for hbo, that would be cool,but not everybody has hbo, which might prove to hurt with the ratings.
I vote adult swim. It would be a perfect transition show from their comedy to action block since it combines both of those in a perfect blend which work really well. (like lupin the third did, it had both action and comedy, a perfect transition show.)