Using Directory Opus is an excellent idea!
The other thing you should do is use PFS3 as it is very much faster than SFS at reading dirs and at the same time it uses less CPU power which means there is more cpu power available to poll that silly gawdawful IDE HD interface.
Another thing you can do to speed things up is switch to a quality SCSI DMA HD interface.
Another thing you can do is to buy a faster accelerator.
But really if you just switch to PFS3 + Directory Opus your dirs will be lightning fast.
Workbench is simply not coded for speed. The underlying AmigaOS is fast but the Workbench.exe is sloooow.
HMMM!!!
My directory listing is plenty fast enough on Amiga Forever running on a Windows PC utilizing an AMD 6 core processor. That listing just zips on by running at 3.2 ghz.