Supermicro chassis in the desired size are the safe bet. If not already in JBOD configuration, you can swap the motherboard for a Supermicro JBOD controller card for a very neat setup. Alternatively, you can hack in a power switch.
I think some people have had luck with Dell MD1200s, but those are going to be more painful to update if you don't have Dell hardware lying around.
I've got a 4U Chenbro chassis I can use, but I'd rather have a dedicated and workgroup/enterprise rig. I have another 4U Chenbro that I'm currently using as a tray, with a Universal Expansion Kit that handles power and has standoffs for the expander: