Quietest 500GB Firewire drive?

Merlocpm, I believe Quadra contains 2 physical 3.5 inch drives. Such arrangement will always yield a little more than twice the noise/vibration of a single drive. That is because it is unlikely that the two drives are perfectly aligned on the same rotational plane. In addition there may be microscopic rotational speed differences between the drives. . . all of this will cause. . . mechanical intermodulation, which will translate into a little additional noise and vibration. Try to place the quadra on top of a sheet of sorbithane. The lower mass of 2.5 inch drives is likely to yield less vibrations. The largest 2.5 inch drives on the general market today seem to be 500GB with 5400RPM rotational speed, with prices as low as $109 for the Hitachi offering. See:
http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=2010150380+1309740009&Configurator=&Subcategory=380&description=&Ntk=&SpeTabStoreType=&srchInDesc=
The drives are sold unformatted and can be fitted into an external SATA 2.5 inch USB or Firewire enclosure for use on Mac, Windows, and LINUX variants. On Windows the only file system supported for large partitions is NTFS

Actually on the 550GB drive it's just the one hard drive. After the lacie, I did try the Studio II edition but that was more noisier due to the many vents and the plastic enclosure. For an external, the Lacie was more quiet. For me though, I decided to upgrade my mini's internal drive to a WD Scorpio. Much better

I would be inclined to put something together myself. The last time I did, I purchased an Icy Dock enclosure. They are a little more expensive, but they are very quiet, good for the drive, and have solid chip sets for USB, Firewire, and E-Sata. Taking this route will allow you to then choose the most reliable drive.

Best,

MP