For a top 30 program, you should almost certainly take more math--and get A's.
How do you know that the letters will be good? Go talk to your letter writers about where you should aim (and what more you need to do). Be clear that you might want to ask them for letters. If they tell you to aim for top 5-30, then you're in good shape. If they've already told you they can write a letter aimed to 5-30, then trust them. The Berkeley faculty know what they're doing.