Angelwolf,
First let me say that $300-$400 cameras will take great pictures and in most instances look just as well in emails and on web pages as the expensive bad boys. Many photos that I've posted on this website were taken with inexpensive digital cameras.
When you are serious about taking photos and want to print high quality photos that's where the difference in camera quality starts to shine. Having full control over shutter speeds, aperture, ISO settings, autofocus points and high-speed continuous shooting.
The Rebel is a great camera but it does not compare to the 20D and the extra speed is well worth the difference in price but you'll get a whole lot more camera in a 20D than in a Rebel.
As Wildman said I would highly recommend buying from Costco as their return policy is so good. If you happen to have problems you return it and get another one. If you buy it elsewhere and have a problem it must be taken to a Canon service center.
Looks like the current price from Costco is $1299 with a lens
http://www.costco.com/Browse/Product.aspx?Prodid=11027052&whse=BC&topnav=&browse=