spidey07, I think you're playing in much bigger-dollar environments than most of us folks around here.
SANs have a high cost to play. The low-end units I've seen really suck, too. So basically, SANs are a great solution if you have a large enterprise storage problem. Small businesses rarely need a SAN at all (internal disks handle things just fine, and usually don't need the features) and medium businesses can't usually spend the kind of money it takes to get a SAN that's worth it.
For small to medium sized businesses, I suggest the NAS approach instead. For a medium to large business, the Network Appliance filers are great boxes - they also have some SAN functionality in them. For a small business, depending on your level of technical expertise in house I'd recommend a Linux/BSD server, or a Thecus or similar stand-alone appliance NAS. Even Windows Server can do a decent job for a small business.
Without understanding better the problem you're trying to solve, I can't suggest more specifically what to buy.
Traditional SCSI is being replaced by SAS at a pretty rapid pace now that all the major server vendors are pushing it. As far as I can tell you shouldn't buy SCSI anymore if SAS is a reasonable option. I would not get the 2.5" disks unless you're really space constrained, they drive price/GB waaaaay up.