Yup, Xerxes from 300 is the same dude from The Book of Esther. In the holy scroll of Queen Esther, Xerxes, is better know as King Achashverosh of Persia who ruled 127 countries from India to Ethiopia...
Xerxes = אחשורוש = Ahasuerus
...and did you know, Queen Esther was 75 years old during the story of Purim which unfolded during a 9 year period.
ויהי בימי אחשורוש הוא אחשורוש המלך מהדו ועד כוש שבע ועשרים ומאה מדינה
The Book of Esther, highly recommended quick read, can be found in any bible, is a marvelous story of a woman savior, female power, a story of woman courage, during a forgotten time of persecution, tyranny, and brutality...
Happy Purim! Hag Sameach!