I just reread your announcement on the other Wellman collections, and I'm retracting my assumption on the next one being Thunstone/Pursuivant. Your comments make me think that it'll be Hok and Kardios collections up next. Hope I'm write.
Out of curiosity, which versions of the older John stories are you going to reprint: the magazine/Baen/Nightshade Press versions, or the Arkham House versions? If I remember correctly, August Derleth asked Wellman to rewrite the stories a little, in order to link them together and make the collection feel more like a novel. Wellman complied, but didn't care too much for the results, preferring the more episodic feel of their original versions.
Interesting that you'll be collecting 'Frogfather' and 'Sin's Doorway' along with the core John stories. I think you'll be the first publisher of Wellman to do so. Personally, I can buy 'Frogfather' being a prequel, but the narrator in 'Sin's Doorway' doesn't really feel like John to me, put that's just my opinion.
Despite all ready owning a copy of Baen's John the Balladeer, I'll be picking up a copy of _Who Fears The Devil_. My personal opinion is that these are some of the most beautiful fantasies ever written, and Wellman deserves to be supported, and be granted a wider audience than what the small press can provide (this is not a knock on Nighshade - their Wellman Library is a truly beautiful thing, but the price point keeps it out of reach of the casual fan).
You've also mentioned that you're considering publishing more Wellman. Can you talk about it a bit? From your comments, I get the feeling that the Thunstone stories (with maybe the Pursuivant stories thrown in for good measure) are up next, and maybe after that Hok or Kardios (the latter series being one I've never read, but really would like to), since you said the third book would be something never collected before.
Hey there. See you're taking requests. I have a few suggestions.
I notice that Manly Wade Wellman is on your list of possible authors. He's one of my suggestions, and I hope that by having him listed you're considering a Hok collection. I read two of 'em in the Echoes of Valor series, and thought them good fun. Wellman also had a second series of sword and sorcery stories about a rogue named Kardios. I haven't read any of them myself, so I can't vouch for their quality, save that even mediocre Wellman is better than most of what you'll find on the sf/fantasy shelf.
Poul Anderson wrote many sword and sorcery and sword and planet stories back in Fifties. He never had them reprinted though, being somewhat embarressed by them, from what I've heard. Baen, or some similar outfit, was supposedly putting out a collection of them, but I read that a few years back, and haven't yet seen such a thing. Again, I haven't personally read these (though I'd be interested in doing so), but several gents at the Robert E. Howard Inner Circle mailing list have vouched for their quality.
I have read Nictzin Dyalhis, however. He's an obscure, but quite talented, writer who published in Weird Tales, writing at least two sword and planet novellas, some sword and sorcery (parallel to and uninfluenced by Howard's own work, to the best of my knowledge) and one or two stories that are pretty much unclassifiable. John Pelan was supposedly trying to put a collection together for his Midnight House imprint, but again I heard that several years ago, and have no idea if he's still considering it. I do think Dyalhis would be a good fit for Planet Stories. If you want to try Dyalhis out, grab a copy of Echoes of Valor III or Weird Tales: 32 Years of Terror, which have reprints of his work.
The Imaro series by Charles Saunders is very good too. Night Shade Books reprinted the first two novels, but dropped the series because of low sales, but Imaro - an adventurer who wanders a gorgeous fantasy Africa - is an excellent character, and Planet Stories may be a better fit for his tales than Night Shade was, taking into consideration your smaller print runs.
Jessica Amanda Salmonson's novels of Tomoe Gozen may also be of interest, though again I can't vouch personally for them.
Jack Vance's Planet of Adventure series, which I just finished reading, would be a perfect fit, though it may not be feasible. While I haven't seen it in the book stores in a few years, they're probably still in print. Still, it may be worth checking into, and I did see Vance in your list.