Nice looking project. I like the idea of covering the cables and providing airflow for your HAF case.
One idea for the server is to put the drives in a separate enclosure. This may require a different controller card that provides an external connection or some long cables...
BTW: WHS does NOT support raid. I spent months trying to get it to work including injecting the drivers right into the install disk. Never got it to work so I just let WHS manage the drives. I have not tried it yet, but my buddy is running WHS2 and is using raid since drive extender has been removed from the newer version.