RAID Enclosure Recommendation

I would like to get a RAID enclosure but not sure which one I should get. I can't afford to fill all four bays so I will get 2.0TB (7200 RPM) x 2 and run it as a RAID-1. Or I might get a RAID that only has two drive bays. Ultimately i would like to have a total of 2TB worth of storage space with some kind of redundancy, using FW800 as the connection.

I am considering:

1. OWC Mercury Elite-AL Pro MIRROR RAID FW800
2.0TB+2.0TB OWC Mercury Elite-AL PRO 800... (ME8SRM20TB64) at OWC

2. Mercury Elite-AL Pro Qx2 FireWire 800 & USB 2.0 & eSATA
OWC Mercury Elite-AL Pro Qx2 eSATA,FireWir... (MEQX2KIT0GB) at OWC

3. Drobo 4bay FireWire 800 & USB 2.0
Drobo 4bay FireWire 800 & USB 2.0 Storage Enc... (DR04DD10) at OWC

4. Newer Technology Guardian Maximus
Newer Technology Guardian MAXimus RAID-1 [M... (GM8QKIT0GB) at OWC

Go with the Drobo, I haven't heard of any of the other ones, but I had heard/read good reviews on the Drobo.