I think you need to go out and try a camera body or two before making your mind up.
The most important thing with taking a picture is the fleshy lump looking through the viewfinder - a novice young lady struggling with 10 grands worth of large bodied Canon D1 and heavy L series zoom lens wont take as good a picture as a confident person holding a camera that is the right size for them that they arent woried about dropping.
Personally I am a great believer in the lenses being the key to good pictures, and as such I am a Canon man as they simply make the best glass. Its not cheap, and often is slightly more expensive than even genuine Nikon, but overall I think any canon lens is better than any other same size and spec lens, and the bodies are all much of a muchness depending on budget whereas Canon probably used to have the lead there as well !!
In general terms with Canon, the more numbers the camera has as a model the less good it is, so a 1d is better than a 5d which is better than a 50d which is better than a 450d. With the middle and lower ranges though the "bigger number" usually means newer - so a 450d is newer than a 400d which is much younger than a 350d for example. Presumably because cameras like this in the most part are aimed at men they tend to get slightly physically bigger the more expensive and desirable they are, even more so as the XXXd series of Canons have a distinctly smaller body to appeal to a wider audience as a kind of super duper point and shoot style camera.
I use a 40d myself, and usually keep whats known as the "kit lens" on it for sightseeing as it goes from 18mm for closesups to 85mm for further away zoom stuff and has image stabilization and high quality autofocus built in - its usually good enough to not miss any particular shots I want, unless at a sports event when you tend to be further away from the action and need more length

. Its called a "kit lens" as it comes as a bundled option if you buy the camera new and you get a nice discount, and is usually well paired to the camera, but not the ultimate quality as that tends to get expensive fast !!
So perhaps try some camera bodies, and then decide if you prefer a smaller body, in which case a modest budget of