Hardware looks good.
Some things of note:
1. Make sure you have a good 100MB ethernet network. If you can, go Gigabit.
a. make sure you use 2 NICS, one from the internet to the core (eth0) and one from the core to the house (eth1)
b. in order for MD's to work, they need to be on the eth1 connection, and using the core's DHCP server
2. Make sure in addition to your media storage, you have a separate drive for the OS and the MD's
a. the base install will be about 20G, and figure at least that for each MD. 4 to 5 MD's = 100G + 20 to 30G for the OS
b. I recommend keeping the OS/MD drive, separate from the media, makes future upgrades non-destructive to your vast collection
3. Make sure you use good network cabling and hardware, intel, 3com, broadcom, cisco, linksys, trendnet etc. bandwidth gets to be a premium when serving that many MD's (I know I have 4), especially when streaming high quality video content.
4. Most DVD's that LMCE rips are of the size 5 to 8GB each movie. Keep that in mind when designing your storage capacity.
5. NAS disk enclosures are great, internal SATA controllers are as well, and always use redundancy when possible, I recommend RAID 5 configurations of 3 to 5 disks.
There is a bit of info for you. I hope it helps.
Always check the wiki and the forums for possible answers and configurations.
Welcome and Regards,
Seth