I finally hit a sweet spot of performance, archive accessibility, and offsite safety, by using internal SSD for latest import workspace, direct attached WD Velociraptor (Thunderbolt) for current projects (can reconnect between Mac Mini server and laptops as needed), and 2 direct attached LaCie 4big Quadras (daisy chained via FW800) for archived projects (up to 32 TB).
Interestingly, because these are all direct attached, BackBlaze will happily back them up offsite at ridiculously low cost if that's your thing. Initial backup of several terabytes will take several months, though.
For fast cheap offsite backups, partner with a colleague with similar storage needs who uses the same ISP via the same head end. Just backup to each other. You can enjoy near LAN latencies at maxed out link speeds. This trick will save you both time and headaches.
Finally consider a product like the CyberPower OR2220PFCRT2U (this one also blends nicely in an AV cabinet) to keep an Airport Extreme and Mac Mini along with all that storage running for about 80 minutes of power outage.