Thanks for all the reply.
Seems like the Samyang 14mm is a viable options.
If I can build my own lens profile (seems like there is a easy to use profile maker/builder) or copy one from someone else, I should be fine. I should only need to correct some of the photo, those with lines that make the distortion very obvious.
I will also check out FA 20mm and FA 24mm. If I can get them with good price. 24mm is a bit too long for K-5, for me, I think.
Stitching is possible, but not for all occasions. I have software for stitching and did play around a bit. Adding some extra steps and effort. Still like to have the one click options available, for scene with moving objects etc.
M20/F4 sound interesting too. Will check out some reviews and price.
Thanks again for replies. Other suggestions are still welcome. Like always, I might end up getting more than one lens.
-kk