I agree with milo. My girlfriend is on staff with Motiv and the equipment that is being sold "on special" or "on sale" would be great for league. Motiv didn't have any really strong pieces until recently so even the "stronger" stuff from the past won't be too strong for league, especially with your stats. The Cruel C51 is a great ball as long as you don't try to drill it too strong. The QZ2 Backdraft could be the best ball they have if it weren't for the Sigma Tour. A combination of those two would be a great league arsenal. The covers are also tunable to give you that extra control over reaction. And just to add one more, the Primal Impulse has a great motion, just not skid flip like many expected. It would be a great league ball once the lanes breakdown and has great carry.
As for the newer stuff. I have always thought Motiv covers come a little weaker OOB than expected. Now, whenever I get a new Motiv ball, I tweak the cover before I drill it. Just be open to surface changes if the reaction you see at first isn't what you expected. Once I adjusted the cover, the ball comes alive. And I'm not talking about drastic changes. I have had a ball come 4000 + polish OOB and I resurfaced it t 4000 + polish and it was better. Something about their polish I don't like. Their power scuff though I do like.