I agree with Brandon about having a mix of Brunswick and DV8. Also, both lines carry just fine as long as the operator is throwing them well. If you like the Diva, the Dude is a good complimentary ball that is a little weaker because of the cover. The Melee has a strong, smooth, predictable reaction that can be used on a variety of lane conditions. The Mastermind is the strongest ball in either line and needs heavier oil to work properly.
If you are looking for an arsenal, I would go with Mastermind or Endless Nightmare as the stronger ball. Then as a step down, the Mystic Aura or Ruckus. Finally as the lanes start hooking too much, a Dude or Melee to control the motion of the ball on the lane.