I found out that it's a different option than either postulated above: The PhotoEngine doesn't like my Daystar P33 50MHz accelerator. Based on this article at LEM it seems that it's possible that the Daystar accelerator and the Photoengine software doesn't like to play together:

http://lowendmac.com/video/thunder4gx.html

"The Thunder IV GX 1600 is compatible with Apple or Daystar PowerPC accelerator cards, but the PhotoEngine software is not. PhotoEngine software will be disabled and should be removed."

A quick test seems to bear this out. So, my IIci can be faster in a general sense, or it can be accelerated for Photoshop...not like I can't disable certain functions through physical relocation of the Daystar Power Center extension and a reboot, but that's kludgy.

Best,

John