here is the complete 90 shiurim, each about 1 1/2 hours long of Rabbi Avigdor Miller, zt’l on Chovos Halavavos in english. you can listem to them online or download them.
http://www.kolhalashon.com/New/HomePage/NewDefault.aspx?Lang=Hebrew&English=True
click on magdei shiurim
click on Rav Avigdor Miller shiurim (its alphabetical, under R)
click on English >> Mussar V’Chasiddus >> Rabbi Avigdor Miller
click on chovos halavovos (the link is written in Hebrew but the shiurim are in english)
edit: i just read your post again, Chovos Halevavos is the same as Duties of the Heart