Much of the afternoon was spent chasing down more information on hardware RAID systems.
My current thoughts are that we can probably get a 2-3 TB (S)ATA RAID system for around $10k. We can put that on a SunFire and either run Solaris 9 UFS with logging and snapshots, or possibly run Veritas filesystem on it.
I found more information on various web sites about the options for hardware RAID, and also found some anecdotal information about how well they work on Solaris. We sites to keep in mind: