A while back we looked at OWC's Accelsior PCIe upgrade, which essentially takes SSD blades similar to what is found in Apple's MacBook Air, and fixes them onto a PCIe card. This allows 6 Gb/sec storage without requiring and taking up 6Gb/sec drive connectors. This is particularly handy for Mac Pros which still lack the faster SATA III interface, plus a bit limited with 4 drive bays.
Sonnet Technology Thursday announced a similar product, but instead uses off-the-shelf 2.5-inch SSDs. The product gives some flexibility of buying just the card and brewing your own solution and also perhaps more flexible upgrades down the road. Trade off appears to be size, as dual 2.5-inch SSDs are much larger than dual blades found on OWC's solution. Also worth noting that capacities on SATA III 2.5-inch SSD drives are currently a bit limited and pricy.
The dual drive Tempo SSD Pro has an MSRP of $299.95 and is expected to ship later this month. The single drive Tempo SSD sells for $149.95 and is available now. Storage is extra on both products. Both cards are PCIe 2.0 x2 and Sonnet says they'll work inside their external Thunderbolt PCIe chassis products.
A while back 
