upgrade from xsi to 40D or 50D. Necessary?

Buy a great lens to get over your craving. I have the XT and every time I wanted to upgrade, I bought a lens instead. Eventually I bought a 5D and because of FF, every lens got wider and I now have the best of both worlds. The XSi is a great camera and will provide great pictures.

i got an xti for similar reasons with various inexpensive glass rather than the new 40d

since then i've upgraded glass and have been happy with the results, now the question is 5dmkII for full frame or used 1dmkIII or 1dMKII s or n

better glass/grip first - then body for specific features

I was in the same boat of ugrade body or stay with the XSi. I picked up a Canon 70-200 F2.8 IS and shot hockey with it along side another person, same lense but with a 40D. I am currently working on a movie for the hockey team with stills from both of us and I think I am going to stick with the XSi since I am seeing no difference in image quality that would make me go change bodies. The money I was going to spend on the body will now be getting me a grip and a 2x Convertor. I am new to the whole photography thing but am learning fast to upgrade lenses first.