Stealth is a different matter altogether, and I'll have to agree with Touch. Don't fire a damn thing unless you're in immediate danger. What can't find you, can't hurt you.
But for the sake of argument...
Midrange, you say? Abandon pistols altogether. Get your hands on a combat rifle, the difference in both effectiveness and accuracy is astounding. In mid/long range, sound is rarely an issue anyway - unless the "other" side has ranged combat abilities too. Like zombies with sniper rifles and WW2 SS uniforms.
I'd only carry a pistol as an OH S**T button, and even in this case, I'd go for a something with firepower, and screw .22s and silencers. If you have to shoot in close quarters, you're already in great, one-inch-from-death trouble.
For close quarters? Get a machete. Or a hatchet, or a baseball bat. A crossbow wouldn't be half-bad, but only carried as a single-shot weapon.
Anyhow, go for stuff that most of the time maim or kill, because pain presumably won't do much to hold them off.