I have several lenses in my collection but no medium wide angle zooms. I own crop sensor cameras as well as FF so I want to stay away from EF-s lenses. My lens of choice would be the EF 24-105 f4L IS but it's a little pricy for the little amount of times I would need a wide angle zoom. I also want a better quality (build and image-wise) than the EF 28-135 IS USM lens.

Any aftermarket alternatives that would be affordable and would produce good image quality? IS is welcome but I could overlook it if the image quality was worth not having IS for the same price.

Thanks.

D