I currently have an early 2008 mac pro 8800 GT with 1 CPU, 8GB RAM, a 7200 rpm WD 750 GB hard drive and a Seagate 7200 rpm 250 GB hard drive. I have run out of storage and plan to add one of the following drives: 1. WD10EADS - WD 1TB Caviar Green (older version is the WD10EACS) 2. WD1001FALS - WD 1 TB Caviar Black Both the 10EACs and 1001FALS drive are profiled here by storage review: http://www.storagereview.com/php/benchmark/bench_sort.php The Green has an idle noise of 35.9 dB while the Black has an idle noise of 41.0 dB. The Green has about 70-75% performance of the Black. I currently have what I consider to be a quiet box (one of my external Lacie backup drives produces more noise than the mac pro) and I would like to keep in that way. While I would prefer the faster disk, I don't really know whether adding a Caviar Black drive to my mac pro will ruin the quiet profile of my mac pro. Has anyone added a Black to their rig without noticing any increase in noise (note I only care about idle noise, I don't care about noisier seeks)?