What do you think is the most powerful speech/statement in act 1 scene 2 and why?

It becomes clearer that Walter's impulses are primarily class-motivated. After describing to his mother how he sees wealthy white men downtown, he expresses a very important principle that is at the crux of the formulation of his identity.

MAMA Son-how come you talk so much 'bout money?

WALTER (With immense passion) Because it is life, Mama!

In this statement, Hansberry reveals that Walter's dreams and aspirations are a perversion of the American dream. The American dream in its entirety upholds intangibles such as liberty, justice, and equality. Walter's version, however, has reduced this dream into the crude, materialistic desire for money.