Hmm 400D or 30D... Image quality will be exactly the same 90% of the time. The difference between these cameras is the available settings. 30D has faster FPS, slightly better higher ISO quality and a bunch of random stuff. Technically it is the better camera. What do you plan on taking pictures of?
My personal recommendation would be for the Canon Rebel XT or XTi (350D/400D). Most of the money and quality in SLR cameras is in the lenses, not the body. I'd get the Rebel XT which comes with a 17-55 lens, save some money on body and spend it on lenses.
Buy the camera and after a month or so see what you enjoy shooting the most then start buying lenses to work with what you want to do.
Get a 10-20mm Sigma if you enjoy nature shots or architecture.
For sure get a Canon 50mm F/1.8, its $80 and you will learn all about Bokeh and depth of field with it, amazingly fun lens.
And if you want to shoot animals or stuff farther away get a 70-200 F/4L. Wonderful quality and versatile lens, second best buy in the canon lineup.
After a while upgrade your default lens. After these 3 lenses you will cover all your focal lengths with great glass and have a decent body. If you stick with photography upgrade to one of the semi pro bodies once you feel yourself restricted by the settings offered by the XT/XTi. Better to learn the slightly restricted body and take full advantage of it than start off big and never learn what extra you spent your money on (my guess is you won't need a 30D for a year or more).
Good luck!
PS. here's a nice link.
http://www.fredmiranda.com/forum/