Aimar if you have a young squad an require some experience.
Cahill if you want a peaking player and are looking for a tidy profit in the near future.
Adrien if you have an existing AM who can tutor (if young enough) or if you are looking for a younger player to break into your squad in 1 or 2 seasons.
Tbh at that state Aimar will be too old, and if Adrien is at a smaller club he won't have improved too much ... but with the right training he would prob be the best option.