I can definitly point you toward some nice restaurants, but ambiance costs $$$, so anywhere nicer than your typical Outback, Longhorn kind of place gets expensive. Ive eaten at a LOT of restaurants, here are some of my top picks. Im not gonna list seafood restaurants cause im allergic to most of it, so i dont eat there...

Sundial at the top of the Westin hotel in Atlanta is nice,(+$100 for two) been there a few times. went there for our 1yr anniversary. Great ambiance, 360 degree view of the city, give you stemware (just one) with the Sundial logo on it. Great food (steak/seafood)

Wildfire by perimiter mall. Steak and seafood. Hands down the BEST steak i have ever eaten, also pricey (+$100 for two), great atmosphere, open kitchen (you can see it from where you sit), been there a couple times, have never been disapointed.

Rays family restaurants (Rays in the city, Rays on the River, Rays Killer Creek) Also steak and seafood. Ive havent been to the City yet, other two arent AS expensive. but still be prepared to leave the better part of 100 bucks The service here is excellent, almost better than the food. but i wont knock the food at all. Occasionally they have live music

LaStrada in Marietta/Roswell, One of the better Italian places ive been to. Smaller, more quaint and nostalgic. Priced around the same as olive garden, but better quality food. and from what i remember, they have the paper tablecloths that you can draw on.