I have a pair of 5850's, the width isn't the issue, nor them touching each other. I have them sitting right next to each other in a crossfire setup, they don't touch, and temp's aren't an issue in my modestly cooled case (decent airflow but nothing spectacular), because these cards stay VERY cool for the power they put out. The biggest issue I had was installing the *&#@ power connectors. For some reason, the folks at ATI, in all their wisdom, decided to put the power connectors at the END of the cards, rather than the side. This made connecting them very awkward in my case. So make sure you have room at the end of your case when you install a 5850. I'm pretty sure a 5770 uses this type of connection too though, however.