@orange,
Have a Mk-III in my 4000T. Still think its time for a faster bus and SATA!
If the faster bus comes off a Zorro III, it is Buster limited to no more than 13.5 MB/s, whereas the MK III and CSPPC SCSI-3 can deliver 35 MB/s off the PCI bus of those devices; in fact, slap on a SCSI-to-SATA adapter and even on an SSD that transfer rate drops to 32 MB/s.
You could move onto NG Amigas and get that bus speed up.