LOL. How the game has changed. Nikon used to bring out a new 'F' series flagship film camera about every 8 years or so, now with the rate of development in digital cameras we're lucky if the latest model lasts 18 months. :shrug:
The truth is is Anton, that the 20D, 30D, or 400D are all capable of doing pretty well all you are likely to ask them, and none of them are going to cease to be useful photographic tools, just because Canon bring out a new model with the latest gizmos. Given the rate at which new models come out now, you're never going to stay ahead of the game without spending an awful lot of money.
Buy the best you can afford certainly, but while you're agonizing over which one, you could be using it and taking great images.
Spot metering is a worthwhile consideration. The larger screen, while being nice, still doesn't enable conclusive decisions about sharpness, you still need your computer to really decide.