12mp Point And Shoot Cameras With Raw Canon Digital Rebel XTi 10.1MP SLR Or The Canon Digital Rebel XSi 12MP SLR? And Lens Question...?

Canon Digital Rebel XTi 10.1MP SLR or the Canon Digital Rebel XSi 12MP SLR? And lens question...? - 12mp point and shoot cameras with raw

I look forward to improve my view and take a good camera. I've restricted it so that the Canon Digital Rebel XTi 10.1MP SLR or the Canon Digital Rebel XSi 12MP SLR. (Perhaps the 30D, but slightly more expensive) I plan to have the only place I want to buy, and I think the 50MM/1.8 EF lens.
Well, here's the thing, I do not really know enough about photography to this decision. I read that you should put your money into the lens of the camera, it is interesting for the extra fork for $ 100 XSi? These properties are much better than the XTi?
In addition, note the lens. I plan on shooting for most social events, weddings, parties, etc., photos and Tourism Travel and perhaps other landscapes. Souvenirs (Nothing professional, just love Nice;)) I will not buy a goal for everyone, but it is a commodity that can easily be used for all?