helle, 400d is just an older model. It's what I have and I got it almost 4 years ago now. 1000d I think is just a newer model a bit higher up than the entry level 400. Now a 5d or even a 1d, that's a camera!
Lenses can make a huge difference too as can a speedlite. I have a 480ex. It makes a huge difference when you can diffuse the flash to the ceiling, makes for better portraits and indoor shots.
Not sure what you can do about the crispness? Do you have a filter on the front of your lens?

