Helicopters with Gatling guns...
Helicopters that work! and gas that is not stale after 15 years! lol
In the preview for the second half of the season they show someone with a rocket launcher. So all they need to do is take down the Helicopter then the amplifier at least will be destroyed and Monroe is back to square one. Even if he has the pendant he will need another amplifier built. If he could copy that Amp there is only one pendant anyways so he can't have more than one running.