Given that you already have an EF-S 18-55mm f/3.5-5.6 IS USM, then I won't suggest you the EF-S 17-85mm variant.
Personally, I would personally recommend the "Canon EF 24-105mm f/4L IS USM Standard Zoom Lens", which goes for around $1,400. It has a constant aperture setting over the entire zoom range, and is a lens that I love using when I'm on trips or whenever out and about. Discount Digital Photographics have them going for $1,389
here.
Alternatively, the Canon EF-S 18-200mm f/3.5-5.6 IS is another possible contender, giving you quite a big zoom range (but without the constant aperture setting as per the previous lens). I believe this one would be similar to the stock lens that you've been using, with the exception that you have a greater zoom range to play with. I have no idea on the image quality for these. DD sells this model for $845
here.
There are more selections on their site - so just browse through and check it out!
The L lens is probably overkill in some ways. But either of these shouldn't be too bad - just depends on what you're really after, specifically.