I use a
Synology DS-409 Slim it is
very small and quiet;
* Takes up to 4 2.5" SATA hard drives (laptop HD's).
* Has RAID 5 support - more
RAID details here.
* Has iTunes server and Squeezebox add-in
* Has in house DLNA/UPnP server not third party licensed from Twonky
* Has audio transcoder in DLNA server along with customizable folder layout for the DLNA client
* All the usuals SMB/NFS/AFP/iSCSI
* Bittorrent client (rapidshare too) via Download Station
* HDD power down feature you can manually set it to spin down HDD's after activity finished so the fan wont be on (it does have a small one in it)
* Power off feature you can tell it to turn itself off at a specific time.
Plus a ton of other features, as a media dump its great at least for me : )
The only catch is that the laptop hard drives top out at 640GB I think (was 500GB when I bought mine) so you'll get roughly about 2TB of storage space tops with all 4 bays in use.
The big plus going for it is that is really quite tiny, imagine roughly 4 cans of lynx deodorant standing in a square shape and thats its footprint. Ideal for placing in a room were you will also be watching content and you certainly wont hear it above the hum of other devices.
If the storage space isn't enough I'd consider placing the NAS in another room even if it meant running ethernet cable and drilling through walls or take a look at homeplugs ethernet over power lines wont deliver the full performance of ethernet but better than wireless. With the NAS in another room you wont have to worry about noise and go with whatever brand/model you like.