etc
Looks like a good setup. I use the WD 1TB blacks in my setup and they are awesome (6x drives, 4TB raid5 with one hot spare) I'll probably grow it to 5TB and lose the hot spare when i need the space.
I know you're getting the RAID card so this may not be relevant but just in case you're interested i've only ever used linux software raid and usually setup four partitions on each drive:
100MB /boot (/boot2, /boot3 etc for remaining drives each one set as bootable and grubbed after install)
2GB swap per drive
20GB linux autodetect software raid
remaining (ie 900+GB) linux autodetect software raid
all the 20GB partitions get put into a raid1 or raid5 for the OS (ie /)
all the 900+GB partitions get put into a raid 5 or raid 6 volume for my storage (ie. /mnt/storage)
this way i don't need a separate drive for the OS, and if a drive falls off the array it's easy enough to boot up off one of the "backup" /boot partitions to get mdadm into action to remove/add a freshly partitioned drive. Add to this fast swap space across multiple drives if your RAM fills up. It's worked very well for me and I move files at about 80MB/s between machines on the network using NFS.
Of course the hardware raid card should be awesome and allow hotswap for failed drives but check if it has linux management software to make the most of it's features, a lot of them i've only seen windows software(drivers?) mentioned in their blurb but like i said i haven't used one so i could be completely in the dark about this.
If you want to use GNOME just download the *alternate* version of the ubuntu install .iso. (alternate lets you play with software raid during the install process). If you're going to use gnome i can't see any advantage to downloading the *server* .iso as its designed for no gui.
Anyway it sounds like you've got it under control. I don't want this to sound like a lecture, i'm just annoyed after a week of trying to get that GA-EX58-UD5 to work how i want and failing. May as well give you forewarning since you mentioned this exact board :D. Until the kernel catches up with these 8111's i'm using this massive case and an i7 with 12gig of ram for my desktop.. pretty stupid hey.
Cheers,
BieRHeDD