And I certainly didn't need any photo editing software with my old film SLRs.
i use PSCS3. i know PSP and PSE are both very good. supposedly Corel has done some major tweaking of PaintShopPro. both it and PSE are under a hundred bucks so that should not set you back too much.. Paint.net and the Gimp are free and are also good. i haven't tried the new pentax software as i'm happy with ACR and PSCS.
my only advice is when you are comfortable with what you find then stick with that program ONLY. why learn 5% of 5 programs instead of 25% of 1.. all of the above have pretty steep learning curves but anything that's any good does also.