ShamSports has updated salary information for the Atlanta Hawks. With 10 players under contract for a total of $65,847,034, the Hawks are currently $7,803,034 over the salary cap and $4,459,966 under the luxury tax line.
Assuming the Hawks fill out the three remaining roster spots with players (either veterans such as Jason Collins and Josh Powell or rookie free agents) who will cost the Hawks just the two-year veteran minimum either in terms of actual dollars or salary cap calculation, the team would be $1,896,799 under the tax line. That might leave room for in-season maneuvering while remaining below the tax line.
The ESPN trade machine has the only published number I've seen for the Traded Player Exception the Hawks got from the Josh Childress trade: $3,631,449. If anyone has evidence confirming or refuting that number, please let me know.