Michael - I (of course) don't agree, Canon is as good as Nikon, everyone has his own favorite one. The 400D is a great camera and you'll enjoy it very much. Rumors say that the 450D (probably this will be name) will be announced early next year so the price of the 400D will probably drop.
Katie - you didn't say what you want from your new lens/lenses, you said you want wide angle, macro and zoom, which is pretty much everything...
Do you want 1 lens, maybe 2? How wide? How much macro?
If you want a simple 1 lens, I think the Sigma 18-200 OS can be suitable. It's not great, but should be good enough (I have no experience with it).
If you want a very wide angle, you can go for the Sigma 12-24 or Canon 10-22, for great macro you have the Canon 100mm macro. But here the price is much higher
And there are a lot more, depends on how much you want to spend.
You can read good reviews on almost any lens in: http://www.photozone.de/8Reviews/index.html