Here's my take on a 16" 9MM carbine. This one was built with the following parts:
-DDLES Glock small frame lower. Quarter Circle 10 now produces an improved version. I's seriously take a look at the NFA/Joe Bob lower - cheaper and has some nice features not found on either the DDLES or QC10 you might like
-Slash 9Q-T heavy buffer and Wolff XP spring
-ALG QMS trigger
-KNS anti-rotating pins
-BCM Gunfighter stock
-Magpul MOE+ grip
-Joe Bob/NFA LRBHO upper
-CCMG Glock cut bolt
-YHM 16" barrel
-Midwest Industries Gen 2 SS carbine hand guard
-Vortex flash hider - recently replaced with an A2 birdcage. A little lighter and shorter, muzzle blast and flash really isn't a problem with a 9MM AR
-Magpul Buis
-Burris Fastfire III on ADM QD cowitness mount
Building your own can start to add up dollar wise depending on the parts you buy. You might want to take a look at the Angstadt Arms carbine if money is not a factor. Hope this give you some ideas and good luck with your build.
Pete