Go with what the wife thinks as she is the one who will mostly be using it. I have the 10D, got it new after it had been out a while and low and behold the 20D came out within 3 months, my typical luck, but still my most used camera.

I have the 28-135 IS lens and it is my most used lens, on camera 99% of the time. I have the 75-300 IS lens, not on camera 99.9% of the time, just don't like the lens at all.

Kit lenses are fine to learn with, but once you start using a much better lens like the 28-135 IS lens you will wonder why you ever started with the cheaper lenses, certainly I thought that.

I have a 50mm f/1.8 lens as well, and that is a great low light lens, although you have to remember it doesn't zoom, so after using primarily zoom lenses, took a bit to get used to it.

Something in the range of 17mm-40mm f/4 L lens would be a very good option as a general purpose, good quality nice optics, every day lens (no not cheap), but certainly will give much better images than the kit lenses do.

I would suggest taking images with the different lenses on the Rebel and on your 20D and then same images with kit lenses and look at the difference the prints are, looking at the screen or monitor sometimes can give you false impressions of quality as well. You need to look at the edges of the image not just the centres as well, to see the light fall off towards the edges of the lenses and also at different apertures to see the differences in quality.

After all, the image is the most important thing. And you can often only get that quality, by using quality lenses.

I wish I knew a lot more that I know now before spending some of the $$$$'s that I have on some of the equipment I have purchased. Secondhand resale here in Australia is terrible so often keeping gear is a better idea than selling it and quite heavy losses. Never know when you might need the back up of a lens or flash etc.

Have fun with your decision.