Since you can't get Kahrs in Massachusetts I won't recommend one for you, although I think you might like them.
On your original list of candidates I own 3 of the 5 - Sig P239, Walther PPK and S&W 642. They each have their place, but for your main carry I would go with the P239. You seem inclined toward it anyway, but it gives you 8+1 rounds of 9mm in a very compact package weighing 27.5 ounces empty. It is reliable and the trigger is very good, lending itself to accurate shooting. I like mine very much and carry it in a DeSantis Speed Scabbard holster. Here is a photo of the gun:
