Quiet Black HD?

I have been trying to build a quiet PC.  I have used several cases including the Lian Li  PC61, the Lian Li PC P50 and the latest the Corsair 800D.  I have also increased the capacity of the Western Digital Black Hard Drives I used in each build from 2-500GB drives to 2-640GB drives and the latest 2-750GB drives.  On the silent PC front I am losing ground on each build.  It seems the 750GB drives generate more vibration than the previous drives.  Is it me or were/are the 500GB drives the quietest of the bunch?  Any suggestions, short of going SSD, on what drive will generate the least amount of vibration?

Thanks all for the input.  In case anybody is interested, I switched out the 750 GB drives and put in a 500 GB drive and the vibration did not change!  So… I finally determined that the vibration from the HD was causing the plastic HD fan cover in the Corsair 800D case to make all the “noise”.  Removed fan cover - problem solved.

Also remember when you mount the HD’s to try to use rubber gromlets or something like that. I use them on my HD mounting screws and it makes a ton of difference. It will cut down on vibration since the HD’s are mounted on metal for the most part. and even for the fans I put rubber between the fans and the case and screws. Now I get no sound from vibrating. The only saud I hear now is just the fan moving air and the HD when it is working hard like when loading games, etc…

1TB WD Black is quiet enough. the silent fan i got is actually more louder then the drive in operation.

Avoid the old 500GB Green Drive if possible… they are slow.