Points only leage? If so maybe you need to replace Beauchemin, and getting Streit would do just that. Depends on the set up of the league, but Plekanec probably holds a great deal more value than the available forwards in an 18 team league.
In points only I make make the trade to get Streit, but if hits and blocks are included I'm content keeping Beauchemin as my third D, and keeping Plekanec for what will be very solid point production.