If you can post it here, we could download it and post our trial times for you and offer advice.
I'm not sure what de-bayering an image is! But generally all of my photoshop CS2 operations take at most 1-3 seconds on a E6400 dual Core CPU, ASRock motherboard with 2GB generic RAM.
The only other support might be if the General Purpose GPU open source initiative launches a plug in for Photoshop (reasonably good probability). If that happened and you had a modern videocard on a PCI express bus - expect your processing times would be 10 - 35 times faster! I'll try asking on
www.beyond3d.com and see what folk think there for you.