I forgot to mention why I chose the more expensive WD RE2 drives instead of normal retail drives.

The firmware on most drives is designed to make multiple attempts when it fails to read data off the disk on the first try. Sometimes taking 20-30seconds before telling the OS about the read failure. In a traditional RAID setup (or RAIDZ w/ ZFS) you would prefer to have the disk report the read error immediately and let the RAID card/OS handle recalculating the data using the redundant copies. RE2/RE3 drives play nicely like this, most retail drives just try a dozen times...and while that happens, Linux/Solaris/whatever may think the drive is dead since it's not responding and report it as a failed, degrading the array.

Also, the RE2 drives have a 5yr warranty and are supposedly designed for the vibration of multidrive setups.

First, let me suggest you consider using a card with a multilane SAS (4x) connector, also called infiniband, instead of an eSATA connection. These connectors are just 4x SATA/SAS bundled into one, so each drive gets full bandwidth instead of pushing it all across one 1.5/3gbps eSATA connection. You can even by a bracket that will combine 4x internal sata connectors to make one multilane sas connector, these run ~$20, so you can use onboard sata for 4 of your external drives if you've got extra sata ports on your mobo.
That said, here's the solution I have running with ZFS RaidZ under OpenSolaris (also used under Linux + FUSE ZFS):
DatOptic EBOX-M - 8Bay Sata Enclosure (other EBOX/QBOX enclosure available with eSATA/MiniSAS/USB/Firewire instead of Multilane SAS)
4x WD 1TB RE2 'Green Drives'
Addonics ADSA3GPX8-ML (SilImage 3124 Based, Certified for Solaris, works in Linux/Windows...MAC?)

I kind of wish I hadn't spent the extra loot on a the 8bay enclosure, since I still haven't dumped a second set of 4 drives, but imagine someday I'll fill it out. The enclosure is simple, no hot swap, just insert bare drives into the bays, no sleds/mounting hardware required.