@ Amesie
Yes, the SCSI on that CS MKIII is better than the SCSI onboard the A4000T. If I was in your position I would not investigate this IDE angle anymore and instead I would find an ultrawide SCSI hard disk for that Cyberstorm. You'll get way better performance.
As a matter of interest, did the IDE drives that didn't work on your Amiga, work on your dad's Amiga?
What happened when you put your dad's IDE drive on your Amiga: did you get the same black screen?
And which machine has the CSMKIII, yours or your dad's?
You should post both configs. I don't know if a CSMKIII has an early config menu like the PPC version, but if it has (try pressing esc on boot) perhaps you can tell us what settings you have in there.