Generally speaking, looking at your arsenal, you're gap in equipment is between the Ulti and Slingshot so I'd certainly look into the Karma Pearl. At that price point, you get a lot of performance from the ball. I'd add a Versa Max simply because it's gonna be one of those balls people want 5 years from now because it is such an awesome reaction.
I had a similar lineup and found the Versa Max and Karma Pearl to be perfect fits between the Ulti-max and Slingshot. They are both incredibly clean through the front part of the lane when the heads burn up. Looking forward to throwing the Marauder to see how it fits in. It's supposed to be longer and stronger than the Too Reckless, which for me was really smooth and less angular on the backend than the Versa Max/Karma Pearl. Although the overall hook potential of the Too Reckless was comparable to the Ulti-Max.
