As I was working on the design, this cropped up in my RSS feeds:

QNAP TS-809 Turbo Pro NAS
Specifications:
Intel Processor Core 2 Duo 2.4 GHz
2GB DDRII RAM
8 x 3.5" SATA I/II HDD, hot-swappable, lockable
Mono-LCD display with backlight and buttons for configuration
As much as I love the idea of owning an NAS I built myself, this is just so much more awesome. So I'm dropping the VIA NAS 7800 project, until something better comes up.
Edit: I've picked up this project again, this time re-imagined as a low-power home storage server. Updates to come in another few months or so.