I think it's crucial to the meaning of the novel that Wentworth be someone who does not come from money -- he's the only self-made man among JA's heroes. Sir Walter and Lady Russell represent the landed gentry of a previous generation -- at their best (Lady R), deeply committed to the serviceable old noblesse-oblige values; at their worst (Sir W), jockeying for status and obsessed with empty distinctions of rank. By contrast, Wentworth and the Crofts represent a new, meritocratic world that is just opening up -- appropriately enough, they come from the Navy (water = fluidity, change) and not the gentry (land = stability, continuity). It's typical of JA's irony that she puts into the mouth of Sir Walter, the most contemptible fool in the novel, a piercingly insightful summation of this issue: he says he objects to the Navy "as being the means of bringing persons of obscure birth into undue distinction, and raising men to honours which their fathers and grandfathers never dreamt of" (ch. 3). Anne's choice between Lady Russell and Wentworth is thus more than a choice between romantic love and filial duty; it's also a choice between two ways of life, two sets of values.