The 10-D is a better camera than the 300D but I don't see how you'd get one with a decent lens for less than $1800+tax. Better, but not $800 better unless you really need the pro features and magnesium body. The CCD and image quality is exactly the same, and the lens bundled with the 300D is reportedly quite good.
If I had the money I'd certainly go for the 10-D, but the 300D is a tremendous deal - assuming, of course, that it's as good as the reviewers are claiming.