With the BW Sting, you may want to have it baked in the Rejuvenator for a little while to draw out any oil thats in the covers. I know that a lot of the Ebonite/Hammer/Columbia 300 balls have been prone to soaking oil up into the covers.
As a stroker primarily myself, good mid range balls you can look at would be the Storm 2Fast/2Furious (already mentioned), or even Roto Grip with their Nomad/Nomad Pearl/Nomad Dagger. All of these have great cores and covers and give you a lot of options on medium oil. I personally throw the Dagger and it's my benchmark ball since coming back to bowling after a 12 year layoff. If you're going lighter, I really like the Roto Grip Rising Star. I also have this and it's a great ball with a great core. The ball carries really well and the hybrid cover helps when lanes start to break down a bit. All of these work great playing more on the outside of the lane but give you the flexibility to move in as well.
Even though I don't throw Hammer or 900 Global, there are lots of great options in their lines as well that you can consider. 2 balls that I have heard great things about from 900G include the Long Shot and Favorite. I also second the recommendations already mentioned with Hammer.
