Hi John,
you might look at these chassis, which are, IMHO, better engineered than that backblaze thing http://www.supermicro.com/products/chassis/4U/847/SC847E16-R1400U.cfm
this supports 36 SAS/SATA drives in a 4U (24 in front, 12 in back) and has SAS2 backplane multiplexers so you don't need nearly as many SAS/SATA cards
The only thing that confuses me about chassis like these is I always miss something that I needed to order to complete the machine. They all come with different things. In the chassis you mention. I would obviously need to still need to buy a mobo, processor, RAM, RAID cards...
With cases like this I need to buy SATA cables too?
I can do a side by side comparison and see what works out to a reliable deal.
SuperMicro seems to be a great company (historically over the years), It seems the chassis is expensive for what you get? (About $1500). Again I should run the numbers for each idea and see how it shakes out. I can report back.
-Jason