I only have one African Grey- Alfie and he is 20 years old now. I have long thought about bringing a second bird home but like others have said, there is absolutely no guarantee that they will like or even tolerate each other. I know that if they had to have separate out-of-cage time because they don't get on then I wouldn't be able to give them both the time and attention they need.
I always think that this is a 'plan for the worst and hope for the best' kind of situation. Are you in the position where you have enough time, space and energy to keep two birds separately if they really dislike each other to the point that they can't be out at the same time?