I'll give it my shot:
1. Musical taste,
2. Listening style,
3. Listening environment.
Musical taste will strongly influence overall system objectives. If your musical tastes do not present a significant acoustic challenge your job is easier. If you prefer symphonic music you will face greater challenges. Your listening style is somewhat related. If you listen at low levels as background music your demands are modest. However if you wish to listen as a primary activity with soundstaging full frequency extension your demands will be much greater. The listening environment - the room, its other uses (if any), and how you and your system are placed in the environment - are the last major influence IMHO.