[CentOS] 10+ TB RAID experiences?

I'm looking for RAID options for at least 10 TB to attach to a Dell 
PowerEdge 2950 running RHEL 5 64-bit Server.

The system will act as a single sign-on server for XP and Linux, thus 
storing user's data from mounted home directories exported from the server 
to various workstations.  It may also house a database.    I'll need a 
storage solution starting at least 10 TB.

Most of the SAS devices I've seen go up to 2 TB.  Looking at the IBM 
System Storage devices, for example, they offer 12 TB and up.

I'm not sure of the budget, so I'll discount cost for now.

How good are IBM's rack RAID devices?   I'm just looking at their System 
Storage DS4xxx line.

How about EMC?  Network Appliance?    Clariion?

Quality of unit, reliability of unit andservice and support, overall cost 
of ownership?    Expandability?

Thanks for any and all insights.

Scott