On photos - outdated version (combination of v1 and v2). STL files contains improved model (v2).
"Sockets holder Back" - print two of them "HDD Cage base" and "HDD Cage handle" - print 5 of each (one pair per disk)
JMS580 is a "USB-to-SATA" converter, so speed limited by SATA-III specs (~600MB/s). You can use base board as USB-NGFF (M.2, Key-B SATA disk) converter, if need.
JMS575 is a "1-to-5" port multiplier. When you access multiple disks - this controller spend lots of time for switch between ports and waiting for result, so speed was much lover, than you expected. For compare: ZFS zRaid-1 with 5 disks (~160MB/s per disk). Read/Write in/to file on ZFS partition. dd if=/dev/random of=/RAMDISK/test.bin bs=1M count=10000 dd if=/RAMDISK/test.bin of=/ZFS/test.bin bs=1M oflags=direct dd if=/ZFS/test.bin of=/dev/null bs=1M iflags=direct JMS580+JMS575: 260 / 200 MB/s (Read/Write) ASM1166: 320 / 220 MB/s (Read/Write)
Each HDD can consume up to 1A on 12v line and up to 1A on 5A line. But 5v we got from 12v line by dc-dc step-down converter (for conversion we use around 40-50% of current). So, we need around 1.5A per disk plus 0.2-0.5A per fan (check label on your fan). So, i recommend 12v/8A power supply. But you can use less powerful PS - just check your disk's power consumption and calculate your consumption, using this formula.