In reply to estivoautumnal:
I've never used simpleyelectronics but I have purchased several lenses through digitalrev.com. I would certainly recommend them as an importer.
I break my lenses down into 3 categories... ultra wide, mid range, and telephoto, if you only want 2 lenses then there will be a compromise.
Ultra wide - 17-40mm f4 L vs 16-35mm f2.8 L vs a 3rd party lens (a compatible tokina etc)
Mid range - 24-105mm f4 L IS vs 24-70mm f2.8
Telephoto - 70-200mm f4 L vs 70-200mm f4 L IS or 3rd party equiv
Earlier someone suggested the 24-70mm over the 24-105mm, I would disagree with this for landscape work. Image stabilizer is worth a whole lot more than 1 stop of aperture in landscape work. Again, for a telephoto lens, I would strongly recommend Image stabilizer if you can afford it, it makes hand holding long shots a whole lot more successful.
Unfortunately with them choices you wouldn't have an ultra wide angle, and if I'm honest, most of my landscapes are taken with ultra wide angle lenses.
17-40mm and 24-105mm would be a good option, but then you don't quite get the zoom you wanted.