If you want a plastic frame pistol, why not consider Glock? A G26, or better for CCW, a G27? And with the Pearce pinky extension (which you will want, trust me) you get 12 rounds in 9mm and 10 in .40. The .40 is a much better defensive calibre too.
I have considerable Glock experience, and my wife is interested in the Kahr so we have been reading up, but I have heard too many tales about how the .40 is less than pleasant in recoil, and FTF's in others. I reckon it is because the Kahr 9mm comes with (or did originally when the K9 came out) a match grade chamber. I know little about the Sigs other than they have a good reputation in general, and while the Solo looks good, I am wary of Kimber and their decisions to use plastic parts in otherwise steel pistols.
For a defensive handgun, I am willing to give up a little accuracy for total reliability. The G26/27's aren't pretty, but they get the job done. They go bang everytime with any ammo you want to feed it. They don't rust, the finish is tougher than a file, and they don't have a bunch of levers and switches to deal with when you draw it. Plus, your backup mag can be a G17 or G22 mag for extra rounds. A big bonus if ten rounds doesn't cut it for some reason.
I really haven't been able to find a better CCW for an IWB rig that I can comfortably wear all day (I use a stiff double thick gun belt and a Milt Sparks VMII --a very good carry rig no matter which small carry pistol you go with) and feel totally confident in that it will work when I need it to.