This has been asked and answered a million times. Saying "the best" is subjective and you can argue what that means until you're blue in the face.
Traffic Jams Motorsports (chris Anderson)
balanced performance (Ed)
are all reputable shops with years of tuning experience and resumes to back it up. Any of those places can take care of your tuning for relatively the same price and produce excellent results.
No reason too make any more post about who tunes best in Atl, those are your options!!!