I find I rarely need to go beyond what you can do in DPP for my 350D. For the 400 you will also find that it can learn where any dust is that has got past the sensor protection and remove it at a poke

The main exception is there is no horizon level tool and occasionally it is worth using NeatImage or similar for final polish and you can do that via PSElements, 4 will do.

generally, such limitations as there are in DPP help one to keep pics realistic. I have even gone back over my FZ7 pics and achieved better results than with PSE in 1/4 of the time.