As far as I can see you could try to attach 1 ssd to SATA0 (it can dangle in the air) and 2 hard drives to SATA1 and SATA2 (They are capped to 300MB/s and should be attached to the case with screws)
There should be space somewhere to put the drives as I can see in the specification. You will probably need to remove the CD drive.
There is also a question if power supply has enough power sockets to attach to the disks. You could try to find eSATA -> SATA adapter to attach something to the last port.
You probably won’t find the bigger case as motherboard isn’t standard size.
I would probably try to upgrade to standard motherboard size but I would also calculate the cost of consumed electricity in a year vs cost of more efficient hardware.
What distro and DE are you using?