Randy and I are going to have fun with this one!!!
I purchased a SAN from Nor-Tech two years ago. It has been rock solid and would recommend them in a heart beat. At that time I purchased a Nor-Tech Voystor 2U iSCSI SAN with five 1TB SATA hard drives for $4451. This gave me 3TB useable (RAID 5) with one drive as a hot spare. If I was purchasing today I would probably see if they had Serial SCSI available since they are also reasonably priced. Here's a link to their site.
I would also look at Drobo. Their Drobo Elite product looks pretty cool and is reasonably priced. They have an 8TB model that retails for $5199, but I'm sure you can buy it cheaper. Here's a link.
The only way to go is to buy a Compellent of course Brian won't agree:) but it is the only way to go. http://www.compellent.com/
One of the biggest reasons that I went with Compellent is because it is the only solution at the time that I could truly grow with. A lot of SANS you have to completely change out as you out grow them, this is true with the IBM solution. With Compellent you can use any drive interface and you can combine different Drives (Solid State). if you run out of physical space you just add on another case with open slots and you don't have to purchase another management device to go with it. So up front it is expensive but I truly believe that in the long run it will be a cheaper and better solution for maintenance.