
Here's more info on my
Sharkoon Rebel 12 build, which is basically complete now.
I call mine a "Rebel 18", as it has space for 18 drives.
With 4-in-3s, you can fit 22 drives, and with 5-in-3s there's room for 26 drives.
The idea was to find a new case and stuff all my old hardware and old drives in to it -- I didn't want to buy any other new components apart from the case.
As as secondary server, it's switched off most of the time and just contains backup data and offline data that's not used very often. Being switched off is good as this thing sucks up a ton of power.
I ended up buying a couple of 80mm fans and a Dual ATX PSU Connector so I could use a second PSU. The primary PSU is a dual rail 500W Phantom and can only power about 9 drives. The second is a tiny 300W PSU from a mATX case, but it's single rail and has an 18A 12v rail, plenty of power for the remaining drives:

Per my previous post, I didn't think the top 3.5" (floppy) bay could be removed, but it can -- I removed the top of the case and the bezel (front of the case) and unscrewed the bay converter:

Here's the result with a 3-in-3 right at the top of the case. Note that the top bay doesn't have any screw holes for 5.25" devices, so putting a single-drive SATA hotswap tray device there probably won't work. Using a 5-in-3 or 4-in-3 device is more likely to work as you can use the holes from the lower bays to mount the device:

The 2x 3-drive cages towards the rear of the case need a couple of 80mm fans to be mounted on the right hand case panel (as viewed from the front of the case). There's no space on the other side of the case for the fans.
Without the fans, the drive temps get very high, even on idle. I mounted just 4 drives for now, as with 6, the drives are spaced very tightly. If I add more drives in future, there's expansion space available:

I used rubber mounts from the
Sharkoon Silencer Kit to mount the two 80mm fans.
The case comes with 1x 140mm fan mounting plate, I bought another two (£3.50 each) to mount a total of 3 fans at the front of the case. I used my existing 120mm fans from my P180. Ideally, you should use 140mm fans as the smaller fans don't cover the entirety of the drives. So far, the drive temperatures have remained in the 20s on idle or light use, but I haven't tried a parity check yet. I'll do one when the case is complete and all closed up.
The top fan plate can't be screwed in without drilling the case with new holes, so I've mounted it by wedging small adhesive rubber feet (from the Silencer kit) at the sides and it's held in with friction and the pressure from the front bezel. So far, it's not rattling at all:

I mounted 9 drives at the front of the case using three 3-in-3 cages from my Antec 1200 and another using a 5.25" to 3.5" converter for a total of 10 drives up front. There's room for another 2 drives there.
At the rear, I mounted four drives in the two 3-drive cages, leaving space for another two drives:

Using 6 IDE drives and 2 PSUs makes the cabling tricky. There's no real space to hide cables either, so this is as best I could get. There appears to be plenty of airflow though, as this is a huge case:

The specs for this server are listed in my sig under "Rig 2"
EDIT: I closed up the two vents over the CPU and GPU and then switched the three front fans to their low setting (they are 3-speed Antec 120mm fans). The rear fan is another 120mm fan and is the only exhaust. That one is temperature controlled.
The system isn't silent, but it's reasonably quiet, comparable to my Antec 1200.
I started a parity check and after about an hour, the drive temps ranged from 30 to 36 degrees. This was a bit of a surprise, as I was expecting higher temperatures. I'm pretty pleased with this case.
This case upgrade cost me (exc. tax)Sharkoon Rebel 12 Fan Frame (5.25") x2 £2.99 = £5.98
Sharkoon Rebel 12 Economy Edition Black x1 £58.49
Ultra Products Dual ATX PSU Connector x1 £6.70
Akasa AK-181BK-2B Ultra Quiet 80mm x2 £4.25 = £8.50
TOTAL (exc. tax) = £79.67 (US$123)