"Desktop publishing." is a variable factor, otherwise you could find the lower specifications are all you need........ Photoshop and all that involves, doesn't need more than a "roomy friendly PC"
Go for underloaded, quality hardware and ideally W2K, or XP if you must, just to avoid "difficult" drivers.
512 Mb of Ram will smooth having several applications open at once, but outright speed as such is unlikely to give discernable benetfit over something quite modest.
A really adequate PSC and choice of case/design to give best cooling. Video card - Provided it will support the highest resolutions and best colour setting does not have to be very elaborate or expensive.
Presumably others will have to use this PC, so include a decent keyboard and a mouse of the main user's choice. Personally I favour having lots of USB ports available.
Avoid gizmos and innovations for this workhorse, remember "If you don't put it in, it can't break and it costs you nothing!"