40D

Is it a lot more camera then the XSi 450

Umm...? The Rebel is a Rebel, smaller but with limited controls. It works well for some people, not for others. The xxD bodies have a bigger size and more accessible controls, which works well for some people, not for others!

The image quality is essentially the same. The focus speed, frame rate, and overall handling is another story. For sports or tracking moving things the 40D is a better camera hands down.

Definitely see if you can get your hands on one. There are some significant design (and size) differences. I think once you use it, you'll never want to go back to a Rebel series (although some people with small hands find it unwieldy). It's especially nice for action photography, as you have more control right at your fingertips. If you can't get your hands on a 40D, essentially all of the xxD cameras have a similar design, so a 50 or 60D will give you a good idea as well. I've never owned the 450, but I still use a 40D, and it's my go-to camera for sports. . .granted, a 1D would be nicer, but that's just not going to happen unless I find a big magazine to hire me who's willing to buy one for me.

Last Thanksgiving I went from an 450D to the 40D and am really glad I did. The 40D feels so much better is my big hands. It took me a little while to get used to the control layout but once I did I love it.

I find that there is a significant improvement in the 40D over the XSi. My 40D still gets used regularly, my XSi has been reduced to only backup duty.

There is a 40D for sale on the buy sell forums for $350.00. I can not imagine a better bang for buck camera anywhere than the used 40D. It fits my hand, produces quality images, and I frankly love the dang thing. I have never owned a Rebel series so can't compare, but when I was looking for a body, I held the latest and greatest Rebel, and it just did not have the right ergonomics for my hand so I bought a used 40D.

With the bigger build and the more accessible/easier controls, the xxD bodies are great if you have biigger hands and also if you like more hands-on control.