Craig Johnson - Walt Longmire series - is another option y'all haven't listed yet. I've only read one so far, but so far so good. I'm really picky about my books; I have so little free time that I'm sure not reading a book unless it's worth the time.
I've read through all the L'Amour books, Elmore Leonard was pretty decent, haven't read Kelton and my online library account doesn't seem to have him either. Nevada Barr is not "exactly" Western but writes a good outdoors thriller, slight environmentalist spin but well worth the read regardless of your stance on the matter.
FWIW I read very few Westerns... my tolerance for B.S. is really low and I can't handle a book with inaccurate ranching or medical situations. (That right there eliminates 99.9% of the Western Romance genre...) The remainder tend to not be well written and so I find myself in the fantasy section of the library more often than not, where the writing is better and I don't expect reality.