The 28-year-old Sim scored a career-high 32 points with 17 goals and 15 assists for Philadelphia and Florida last season. The Flyers traded Sim to Florida on Jan. 23 for a sixth-round pick in the 2007
Sim has appeared in 230 NHL games. He previously played for Dallas, Nashville, Los Angeles and Pittsburgh.
The 23-year-old Popovic was scoreless in seven games with Atlanta last season, when he also played with Chicago of the AHL. Popovic, who was acquired from Anaheim in 2005, had 12 goals and 26 assists with Chicago.
Stuart, 24, had 13 goals and 14 assists with Chicago last season.