For a system that is used to scan, edit & print photo's would a single or a dual processor system be the way to go?
I would like to be able do all three tasks at the same time with out the system being slugish. The average file size would be about 15-25 mb.
Yeah the newer generation processors are more then enough to satisfy your needs, either AMD or intel processors can handle that with no problem, get p4c 3ghz or a A64 3200+ CPU, and you will be set, the only thing i would recommend is at the minimum 512MB of system ram, and a 128MB video ram graphics card, other then that i cant think of any reason why a little photo processing cant be done on a single CPU core.
This task can be done on much less computer without any problem, if you want ultra fast performance go with my recommendation, it may be slight overkill but o well.