The only "spare" machines I've got are some crusty beige-box PIII-500MHz's at the office, where one by one they've been failing and we've been scavenging parts to keep them going. That's not a good starting point for a RAID box...

Instead, I've decided to go with the Infrant ReadyNAS solution. For what it's worth, there's an AVS forum thread where they are organizing a "power buy" which will apparently get Infrant's next-generation "X-RAID" technology that will apparently be a standard feature in their products next month. The gist is that you can incrementally buy disks, plug them in, and their RAID controller does all the work.

The price on the power buy wasn't posted on AVS, but it's supposed to be posted on a private forum on Infrant's chat forum. As soon as I have numbers, I'll post them here for anybody else who may be interested.