Can't you just jab it into the guys temple or something?
Only if you want the knife to get stuck. Accross the throat works, but is not exactly quiet, and is incredibly messy. Base of the skull is better, but it's a smaller target, takes a lot more force and your knife can get stuck there too. Pull back the head and put the knife in under the chin through the roof of the mouth is good. Instant kill, not much blood, no sound, but a hard move to pull off. I still say it's easier to smash the throat with the bladelike bone on the base of the thumb, put a proper two-handed choke hold on while moving backwards to get the target off his feet and lower to the ground. 5 seconds - unconsious. 7 seconds - dead. If you need to finish them off quicker, apply choke hold as above, throw your feet out from under yourself and slam you shoulder into their head as they hit the ground. Snaps their neck like a chicken bone. Rinse and repeat on next tango.
As far as supressed weapons go, loud guns are for impressing other gang-bangers and shooting deer. Anybody with combat experience will tell you quiet and quick is the way to kill other people. You don't get them first, they get the chance to get you. Don't give them that chance.