League One sides Bury and Peterborough United are also said to be courting Nicky Clark, who is leaving Ibrox this summer.
Clark (R) is a man in demand
Fellow League One sides Bury and Peterborough United are also said to be keen on the former Aberdeen trainee, who will leave the Light Blues for nothing this summer.
Barnsley manager Paul Heckingbottom and assistant Tommy Wright lift the League One play-off trophy
Clark, who is the son for former Gers striker Sandy, arrived at Ibrox from Queen of the South three years ago and registered 24 goals and 14 assists in 110 appearances.
The 25-year-old's exploits helped Rangers to two promotions and he leaves having led the Light Blues back to the top flight.
Southend - who finished 15th in League One last season, one and two places behind Bury and Peterborough respectively - have released former Republic of Ireland international Noel Hunt, while another striker Jamar Loza has returned to Norwich City following a loan spell.
Brown's Shrimpers ended the campaign 15 points off the play-offs
Rangers are expected to add to their front line following Clark's release.
Kenny Miller, 36, is one of only three seniors strikers left at Ibrox