Anon, I'm actually trying to help, but even though you're starting out, please don't begin with this kind of mindset. Some dubs, examples being Cowboy Bebop, Black Lagoon, and Hellsing, are great, and in my personal opinion, better than the original. You just have to find the right ones.
Now knowing more, I'm going to add to my list, (The one recommending Kaiji, Mononoke, etc.) with Eva, Lain, Perfect Blue, and Vampire Hunter D.
Also, while Gurren Lagann doesn't have a "dark atmosphere", I would highly recommend that you watch this. It's great.
Hope I could help?