You could do well without using steroids... You don't sound at all fat... If you have a solid training program 4-5 days of weight training a week and 3, 45+ minute cardio sessions and grab yourself a good ECA stack (dymetadrine extreme is one of the best out there) you should start to see quite a bit more defenition.
You would also need to make sure that your diet is in good order... Stay away from junk foods, sugary stuff and fast food.. I'm sure a lot of guys will say the same thing... You don't really need gear to do what your goal is, just some good ol' hard work!
YUM