I've been using the Sims S-Coil for the past couple years and really like it. In fact, I just put one on my new bow and picked up one for both my dad and my best friend.

At $13.99 a piece, you can't really beat that price, especially for how well they work at dampening sound.

If you're looking to both balance your bow and to dampen sound, check into Stealth. You'll pay a bit more, but they're also worth the money.