I just picked up a 4u supermicro chassis that holds 36 3.5" disks and 2 2.5" disks.
Unixsurplus.com has some pre built ones for truenas (I'll be running unraid.) I'm moving from a 12 bay dell with 200tb useable. Once I max out this new chassis, then I'll be adding a jbod shelf. Those can basically double my storage without having to do much.