Get Epic Loot, Digitalroot's Epic Loot Adventure Bounties+all the required/recommended mods that add new enemies(MonsterLabZ, RRRMonster, Monsternomicon, etc., and their requirements)+configure them properly, and those new enemies should show up as bosses in the bounties, as well as normal versions in the world.

CreatureLevelAndLootControl can also give enemies and bosses special effects to make them more interesting to fight, and be configured to support the modded enemies.