hmm.. i would think that a heavier and thicker case would be better for acoustic performance ..
I have a case that's exactly the same as that antec 4u case above (probably oem'd from same source), save for a slightly different looking front cover here
and while i haven't put it together yet (papst fans just arrived), here are my observations:
* good front ventilation, all drive covers stamped with holes, with holes getting larger towards the sides of the bays (foam filter on case cover).
* front 120mm fan in enclosed in a 5-1/4" drive cage, so less turbulence and all of the airflow goes over the drives
* also means that you can use a zalman hdd cooler to effectively cool fast drives like 10k and 15k rpm hds while still having a slow speed 120mm.
* because all drive bays are ventilated and the right side mirrors the left, you can either swap sides having the fan on the right and seperate out your agp/pci slot area (i see this on some dells) with some barrier or keep it as is and have a dedicated airflow path to the power supply using an empty right side drive bay or shroud to the cage.
* 1.2 mm steel feels good