I'd take KJ Wright and B-Wags over Lee, Smith, and Vander Esch.
It's close-- but I wouldn't swap them. When Lee is healthy he is as dominant a player as either of those guys (IMO Lee is the smartest LBer in the league in the way he diagnoses and understands what an offense is doing on any given play)-- and both Smith and LVE's ceilings are higher due to their rare athleticism.
Wright and Wagner are proven commodities-- but they have also had the benefit of playing on a talented, loaded defense for years. We'll see how their production fares now that the Hawks are trimming their payroll. Lee has played virtually his whole career being on a mediocre to bottom 1/3 defense year in and year out.
The defense in Dallas is now more stocked with talent than it has been in quite some time. If Lee can stay healthy (huge IF, I realize)-- then this D can really start to carry it's weight. With him healthy last year, they were giving up under 20 points a game and under 100 yards rushing-- both very solid numbers in today's NFL.