I definitely want your input on this but here is my concept, especially considering your dudes seem pretty tough.

The setting is Modern-day, we could go for futuristic but for all intents and purposes, Modern is what works best. Most countries are aware of the brother's power and are afraid of that getting into the wrong hands. Shortly after they complete a hit in America, the CIA begin plans to covertly eliminate them. A trap is hatched, where my team is waiting for the brothers to return to where ever it may be they are currently staying, preparing an ambush.

If you want to up the ante, a couple of grunts could be with the team but I see this as a hunter becoming the hunted scenario. These tough vampire assassins having hired killers coming after them.