can you at least explain WHY they're better than the XT series?
The 30D has a slightly bigger viewfinder and better organized menus, buttons, and dials. That's the main differences I see, and they are worth an extra $200 to me, but I think image quality differences between the XT and 30D, or even 40D, are insignificant if you know what you are doing.
Here's some good advice to beginners about purchasing cameras and lenses from H.P Robinson, a famous English photographer. Moderators this is public domain material, and not copyrighted.
"The lens is always considered the most important of all the tools the photographer employs. So it is, but I should like to say boldly that, within limits, I do not care what make of lens I use. It is as well to have the best your means will allow, but there has always been too much made of particular variations in the make of lenses. It has been the fashion to think too much of the tools and too little of the use made of them. I have one friend who did nothing last year because he had made up his mind to buy a new lens, and could not determine whose make it should be, and he was tired of his old apparatus. His was of the order of particular and minute minds that try to whittle nothing to a point. I have another friend who takes delight in preparing for photography, and spends a small fortune in doing so, but never takes a picture." from H.P. Robinson's "Letters On Landscape Photography" published in 1888.

I think it's funny that as much as things seem to change, they really stay the same. I don't know what brands they were arguing about back then, but I'm sure old H.P. would recognize the Canon vs. Nikon debate.
Here's a link to the entire book online. It's the best photography book I've read all year.
http://www.archive.org/details/lettersonlandsca00robirich