The Defense of Marriage Act does not need to be repealed to provide full economic and legal equality for same-sex couples. Rather, consider its actual language: It defends the definition of "marriage", retaining its millennia-old meaning.
As the alternative: Eliminate "marriage" as a legal concept. That is, substitute, in every law and regulation, at all government levels from federal to local, the term "civil union". Create that as the legal definition of a "family".. Then, what most call by the word "marriage" would be simply a personal label for their particular form of union.