I just had to return my Radeon 5770. It corrupted my BIOS and my OS and it took a week to figure out it was the GPU causing the problem so I'm a little hesitant about another Radeon product. I also regretted not getting a better performing GPU afterwards.
if you are using designing software then stay away from radeon cards. They are exceptional for gaming but when used proffesionally they can bring you a world of hurt.
What do you consider designing software? I use photoshop which is part of a designing suite. And what do you mean used professionally? I'm a professional photographer who uses photoshop on a daily basis.