The only two I know of are Assent, and Opus. Both are in the Lenox Mall area of Buckhead. I haven't dug deep, but it looks like Assent expects you to come in with your own knowledge and chips, while Opus gives you some training and some money.
From what I read Assent is the real deal. Haven't heard much bad about them. Most people like their platform.
I haven't heard anything (good or bad) about Opus.
i'm not concerned with the actual firm just the space and availability to hook up with appropriate connections, systems etc like trading systems and bbg.
what building is ascent in ? i know opus is in AFC.