scary

I'm junior undergraduate at top 15 undergraduate US university double majoring (two BAs) in Computer Science (top 30 dept) and Economics. Right now, I have a undergraduate GPA of about 3.2 and figure I can get it to maybe a 3.4 by the time I graduate. I had a pretty much mediocre freshman year GPA (~3.0), but my sophomore year GPA is considerably much better (3.4). My Econ GPA is about a 3.3 and it probably won't go much higher since I only have 2 classes left in my major. I can probably get my CS GPA to go from a 3.4 to maybe a 3.6 since I have about 5 classes left in my major. I haven't taken many math classes (calc 3: b-, stats: b+, will take discrete math and maybe linear algebra). With all this in mind...I'm interested in getting a phd or masters in computer science, economics, or business...somewhere they all meet. (think: operations research, game theory, artificial intelligence). My ultimate goal is to get into a top 20-30 program, but I know with my track record it's probably not too realistic. However, I think I may have a shot at a top computer science masters program and maybe do research there. I should be able to ace GREs (close to 800 math...600s verbal) since I'm a good test taker and have always done well in math. What do you think of my situation? Do I have a realistic shot at MS programs such as Stanford, UMich, etc.?