So, I've been shopping around for good prices on 300 and 320GB drives, and for rackmount cases with hotswap sata trays. The poll below is based on the price of drives and cases, and doesn't include things like motherboard, processor, ram, etc. I consider those to be more or less fixed costs, since they'll probably be the same no matter what I end up doing for case and drives.
The big question I'm pondering is this: do I buy a case that'll hold 12 drives, and cost less, or do I buy a bigger case, so I can build a second (or third) array into it later and only need to buy the drives. If I get the smaller case, then next time I want to build an array, I need to do this whole thing again. The larger case will cost more money, which isn't prohibitive but still a consideration. But it's also a /larger/ case. More of a pain in the ass to deal with.
What's the best option?
3U Case, 12 bays, 12 drives - 3.52TB for $2250
5U Case, 24 bays, 12 drives - 3.52TB for $3350
5U Case, 24 bays, 24 drives - 7.36TB for $4800
6U Case, 36 bays, 12 drives - 3.52TB for $3650
6U Case, 36 bays, 36 drives - 11.2TB for $6550