Can't give you any specialist lens knowledge but for what it's worth, if it's helpful dwarfer16, I bought my 350D with the kit lens and a Sigma APO DG 70-300mm zoom. I'm very happy with both lenses.
My point is that I think you'll enjoy having a big zoom lens, but I suspect you'll be happier with one big lens that covers most of the range so you don't have to swap. That's the only problem I have with them. Something 28-200 might do better than the 2 lenses.
But have you considered what you want to photograph - are you interested in macro photography, for example? At work, we've just bought a Canon Ultrasonic EF-S 60mm 2.8 macro and I'm astonished by it. It's in front of me now because I've borrowed it to try over the weekend.
So if you haven't considered it, maybe you want to spend some of your budget on a good broad zoom for lots of purposes, and also on a specialist lens, like a macro, for example. (Although I think this one cost the best part of £300 by itself.)
Just something to think about - you have a DSLR, don't stick with one lens!
DM