If you are looking for a step up anything in that medium-light grouping would work, but it really depends on how much more oil you may be seeing.
For instance the Brunswick Strike King is supposed to be the replacement for the Slingshot but its a bit more ball than the Slingshot, Ringer would be a step up from that. Karma is also a very nice ball if you can get your hands on one ( just stopped making it)
Ebonite has the Cyclone which is a damn good ball for the money.
Storm has several in that category with the Tropical Heat ( I think its the Heat I usually get it and the Breeze confused), and the Lights out.
Columbia has the Freeze line and then maybe the Disruption.
Hammer has the Cobalt Vibe and then the Arson Low Flare ( just bought one of these myself and can be adjusted for lots of conditions according to most users).
Hook series from 900 Global is said to be a very good line, although haven't personally used one myself.
Track 300c series might be a good fit, but I don't know the line as well so someone else might be able to fill in on that.
Radical has the Torrid Elite and Torrid Affair which I almost bought ( and might eventually).
I know I probably left some out but thats a pretty good list to start with I think lol.
There are a ton of balls in that category and was advised to me, there isn't that much difference so find one you like the colors and price on and go for it.
