[Stinkeypete]

Since I purchased my Canon 20D back in 2006 I have been using the EF-S 18-55mm kit lens that came with it. Whilst this has served me well, and i've had some great results from it, I am looking to upgrade.
Ideally I would like to go slightly wider than 18mm in order that I can achieve the equivalent of approx 20/22/24mm if my sensor were full frame. At the other end the 55mm has been sufficient for my needs.
Recently I borrowed an L series Canon lens (24-105IS) and the difference in quality was evident. However, this is the only comparison I have at the minute so I would welcome any and all opinions/experiences/suggestions please. Essentially I would like the quality of image that an L series provides but would like to know if I can get that with an independent or just one of the other cheaper Canon lenses.
Most of my photography is Landscape.
Many thanks
Paul