Yup, as already mentioned, A4000 IDE is slow.
PowerFlyer/FastATA4000 is faster, but still uses a lot of CPU power.
The best option is SCSI, but this may be somewhat expensive and hard to find.
Options:
FastlaneZ3 (Zorro3 board)
C=A4091/DKB A4091 (Zorro3 board, needs buster rev 11)
Accellerator cards like the Cyberstorm and GVP boards.
(Note: The Apollo boards have a SCSI controller, but this is absolutely useless)
Or simply keep the A3000, it already has SCSI.
-Paul
EDIT:
btw AFAIK your Buddha board is just as slow as the A4000 IDE.