Since I haven't seen any other mentions of it, I'd point out only that anime is full of vampire-related stuff.
I know plenty of people who loved
Vampire Hunter D - I can't really comment on it because I've never seen more than snippets. But I have seen the first season (so far) of
Hellsing, and much of it is fascinating, and may be very familiar to AtS fans. Picture a 'verse in which Angel turned Kate to save her from an on-the-job shooting, whereafter she has to come to terms with the world he (and now she) inhabits - including the semi-secret vampire-hunting cabal of which he is a part.
A certain amount of screen time involves the lead vampire's ongoing attempts to teach the lady cop-turned-vampire how to survive and adapt, but the most interesting relationship is between him and the human woman who runs the Hellsing Organization - i.e., the above-mentioned semi-secret vampire-hunting cabal. (Something which may also sound familiar to AtS fans.
)
I would offer this caveat, and that is to watch if you can in Japanese with English subtitles. I'm no original-language snob when it comes to anime, and most English adaptations I've seen are plenty good enough for the material, but the
Hellsing dub is damn near fatally wounded by a truly, epically awful performance in a major, major role. I'm not kidding when I say it could kill the experience for you; one reason I've only seen the first season is that I'm waiting until I can get hold of a non-English version of the subsequent episodes.