you sure have a lot of options...(and as mentioned, you can't go wrong with the kimber).
since you already use the glock 17, a viable option is the glock 26--though it is not really all that small--an advantage is that you already know the manual of arms, and its fairly reliable. unfortunately, no second strike capabilty though. for range work/drills, you can also use your g17 mags--which you will grow to prefer at times.
the kel tec pf9 and p 11 are reasonably good too--unfortunately, the keltec pf9 has a cross slot in the dust cover, which can be a real problem for snag free draw if you opt for pocket carry--while the p 11 dustcover is smooth. more importantly, the p 11 allows you to have second strike capability in the event of a harder primer and failure to fire--a great advantage over the pf9. this is a feature i feel i must have in a defense piece--to have second strike capability on a primer (as per usual procedure, you may simply rack that round out, but if the unfortunate event that the next one on tap has a hard primer also, you're back to square one--whereas in the situation of a former strike on a hard primer, the second strike can often tip the balance).
those primers are not as much of an issue now, unless you use some harder primered 9mm ammo intended for some other systems. though it doesn't crop up very often with most full size firearms, as you move into smaller guns whose hammers are have less mass, or smaller striker fired guns--it should be in the back of your mind--it could happen.
back in the early 80's, i used some factory speer lawman ammo in 357, which had very soft primers--and the loads were quite hot. i would often get primer metal flowing back into the firing pin bushing--subsequently tying up the cylinder. the eventual solution was harder primers--which helped remedy this situation. but, around this time we began to see striker fired semi autos such as the hk p7, and the glock arrive on the scene. i remember having quite a few failures to fire with some of those early glocks (1989-1993), due to those harder primers, and one cure then was to use ammo with either federal or winchester primers--but since then this problem has been largely remedied.
but it can stick in one's mind...
i prefer the hk p7, and have used same for 24 years--though it is too heavy for some carry situations, and it could never really be a pocket piece. with the keltec p 11 you can utilize a stainless steel belt clip which you can attach to the side of the frame--so for some situations you can use same, and the need for a holster for the lightweight is eliminated. i use that system for some carry situations.
have not yet used a ruger lc9, but as per usual, their wares are always good--but sometimes its wise to consider waiting about a year...
