Our previous work on improving the quality of object-oriented legacy systems through re-engineering proposed a software transformation framework based on soft-goal interdependency graphs [11]. We considered a class of transformations where a program is transformed into another program in the same language (source-to-source transformations) and that the two programs may differ in specific qualities such as performance and maintainability. This paper defines a decision making process that determines a list of source-code improving transformations among several applicable transformations. The decision-making process is developed on a multi-objective decision analysis technique. This type of technique is necessary as there are a number of different, and sometimes conflicting, criterion among nonfunctional requirements. For the migrant system, the proposed approach uses heuristic estimates to guide the discovery process.