If you never work with offset printers, then I'd choose either PSP or, if you choose the Adobe route (why should you?) get Photoshop Elements. If you own a digital camera, I'd invest in a good noise reducing plugin like Imagenomic's noiseware.

It's usually better to follow a route than to confuse yourself by starting all over because you think that that other road is easier or better. And once your work in ready, no one can see whether it's done in the Gimp, PS, PSP or whatever. You don't need a truck to go on holiday.