Just built a new system using the Antec Sonata Case. One of its best features is its incredible sound insulation features. The fans and hard drive enclosures use rubber mounts and the fans can all be set for controlled power management to maintain all the components ideal operating temps. This is the quietest PC I've ever built. Really nice unit highly recommended!
Here's a a full spec review:
http://www.arstechnica.com/reviews/0.../sonata-1.html
