Thanks to everyone for their suggestions.
My decision has much to do with my own trail of tears here, what I already have in my bag and what seems like a place to fill... than necessarily, as it differs from what works for others, a reflection that anyone else's decision or input wasn't helpful. This was a very hard decision full of much agonizing because... seems there's something everyone dislikes (and strongly dislikes) about each of the lenses that ended up in my final running.
Because I already have a 35mm, a 50mm and a 70mm, I really didn't want to duplicate an existing focal length. For me, this cut out the Sigma 70mm Macro which by all accounts would otherwise be one of the most desirable out there. I also perversely found myself drawn to wanting to go with as many primes in my bag with the same 49mm filter size. Call me lazy, but it was something I looked at. Next I thought of weight, and lighter as better. Finally, I focused on opinions regarding sharpness and over-all score. Frankly, over-all isn't quite as important as the other IQ ratings... but a lot of folks don't actually fill those out. And as I said, seems the Sigma 105, the Tamron 90 and Pentax DFA 100 WR all had crummy handling issues... or some annoying feature.
Increasingly, I'm shooting hyper-manual mode on my K-5, so I decided even the focus thing was livable - especially in macro. I do like AF, so I want it available, but if it ain't, I can live with it. My decision to get back into this DSLR game... after getting burned on a Leica digital rangefinder long ago... was that IQ basically had made it to a level consistent with film at a price where you didn't have to be a king in order to play. I'm okay with not being Mr. Automatic. Think that's really the norm here for everyone... only it's "nice" to have the focus ring move by a button, rather than lose time focusing. At worst, reversion is awkward or less than optimal... if other camera options don't have to deal with it... but not a deal breaker if it's only one lens that can't find it's way out of a paper bag.
So that's the thinking that led me here, and led me to seek out the best deal I could find on a used Pentax 100mm DFA WR on ebay. Will know whether I managed that or not when I see it in a week or two. But for now, thanks to everyone's help, I think I've got (or should have) the 100mm-and-under focal lengths covered. I'm reading about the long end, but for now, sticking with my 50mm-200mm kit zoom seems good enough to end LBA until a wildlife trip prospect emerges... which I'd hope for in a year or two. In that regard, the 300mm range seems a real additive... but maybe it's rentable as a 1st try.