For a gaming pc with a long video card and a tall 160mm tower style heatsink you will need a case that is at least 19 inches in length from front to back and width of at least 8 inches.
I have the Coolermaster HAF 932 which is huge beast. It can accomodate any cpu heatsink and video card made. Ventilation, airflow, and cooling are excellent. The exterior design is something you either love or hate.
For a more classic look the Antec Twelve Hundred is a suitable case.