Pick one. Most of those are good, but they will list all the features you should expect in such a device. IF anything, it will give you a place to start researching which you like beter feature wise, and cost wise.
You did not mention how much you plan to spend. Raid 5 arrays generally yield a capacity of total - 1 drive, for parity. So 4 500gig will yield ~1.5 T. Now if you are doing raid 1, 2 will yield 1, but you take a performance hit.
Are you planning on building your own, or buying one. There are many BYOD units.
I own a Snap 4500 with a Snap10 expansion unit. You will find that most older systems have not been tested with the new high capacity drives. I have 4 400gig in my 4500, Raid 5 yield 1.03T. The 4500 has 2 gigabit ports, the Guardian OS supports auto shutdown by APC, network management card. The 4500 has supports for iSCSI, 2.4 ghz P4. The Snap 10 can be used for expansion or for hot spares, can mix and match. Snap also has software to allow 1 servers to sync to each other. All drives are hot swapable.
Snap Is now owned by Adaptec. The newer models have a performance boost. Using SATA vs IDE drives. These systems are not cheap, but you are buying enterprise equipment.
There are may system to choose from, All depends on what budget you have.