Help me out...

The budget allows for an upgrade now, but I neeed some help. I can get either a 350D or a lens. Currrently, I have a 300D and the kit lens. Like it has been said here many times, I think the kits lens is pretty decent, but I want to step up a little. The lens I have in mind is the Sigma 24-135 2.8-4.5. It has some low dispersion and aspherical elements. Can't afford L glass right now.
The question is, which ONE will do more to give sharper, clearer, just generally better pictures, the lens or the higher resolution camera? (Eventually, I'll get both, but I can't right now.) I think I know, but I want to hear the opinions of some very knowledgeable photogs here. Most of what I do is landscapes and wildlife. I already have a pretty decent telezoom.

It's been said here many of times, upgrade the glass before upgrading the body. There will always be a newer body that has better resolution, but good glass should last you a lifetime.

I can't speak to the quality of the Sigma lens (I've owned a few in the past, but now I have just Canon), I would say buy quality glass until your camera can no longer do what you need it to do, then consider upgrading the camera.

The 300D is still a very good camera and, for practical purposes, ought to give as good a definition with a kit lens as would a 350D.

If you want to improve results, go with a better lens.

get a new lens. what's the budget anyways? although not as fast, the canon 28-135 IS might fit the bill as well. many have it and like it. also there's the tamron 28-75, which would match your sigma selection for speed, but at a cost of focal length.