When he comes down out of the mountains of West Virginia as a young man, Sutpen realizes that not only are blacks considered inferior to whites, but poor whites are considered inferior to rich ones. (As he bitterly learns at the door of the white man's mansion, not all whites are created equal.) Because Sutpen comes to Jefferson without any social connections or money, he must marry into them: he believes that having money and the right wife will bring him power. He's definitely right in some respects, and he gets his rags-to-riches story, but at what cost? Absalom, Absalom! is clearly a story about the danger of racism, but we can't forget about the classism that tinges the whole story, too.
Sutpen's preoccupation with social status is second only to his concerns about race.
Rags to riches? No way. Try rags to premature, violent death.