DSLR Upgrade Question?

[defected_v]

Just recently, my Canon Rebel XT broke and now I have to upgrade. I need a camera that will give me high quality photos. I like taking portraits mostly. I was thinking of getting the 40D but it's pricey. I want to know if it would be better for me to get the 40D or Rebel XS or XSi?

Will I see a considerable difference in image quality?

I was considering even getting a Nikon, but I think the lenses are a bit more expensive?

Thanks so much!