You mention that "Philosophic traditions down from the Greeks have constructed arguments to conclude that just acts are good for the agent (the self)." A good example of this can be found in Cicero's book, On Friendship (Laelius de Amicitia). In it Cicero states that "the very essence of friendship" is "a common set of beliefs, aspirations, and opinions." (p 31). He further states that friendship is only possible between those who "act and live so that their lives give proof of faithfulness, integrity, fairness, and generosity; and who are free from any low passion, greed, or violence; and are of great strength of character," (p 37). Most important for true friendship, however, is virtue and "virtue, too, loves itself," (p 165); in conclusion he states, "I say it is virtue that creates and preserves friendships. Virtue is the source of compatibility, stability, and permanence." (p 169)
Cicero's stance would seem to be one that in most respects is consistent with Rand's view as it prominently does not depend on "service above self", but is consistent with integrity and treating others with respect while acting virtuously.
Quotes are all from How to be a Friend: An Ancient Guide to True Friendship by Marcus Tullius Cicero, trans. by Philip Freeman. Princeton University Press, 2018.