Stick to cases that support 120mm fans rather than larger fans, especially 200mm. Cases that shroud the fan rather than mount it in a large meshed panel provide better airflow in my experience as it reduces flow reversal around the frame of the fan. The best case i've owned for air cooling was a Corsair 550D, leagues ahead of the 600T IMO.
As much as people like to insist that direct airflow paths and meshed front panels to reduce obstruction improve airflow the difference is really minor compared with just have a well balanced set of fans that are nicely set into the case.
JR