If you can only use 2 balls, I would suggest the Reckless as your main ball so that you can adjust the surface by taking it to 1000, 2000, 4000 or using polish to help it get down the lane.  The Nexxus or Revenge would be good choices as well, and both take well to changes to the coverstock but are stronger overall than the Reckless.  The second ball might be a too reckless, a misfit, or the pink/purple karma.  All three of these balls go longer and make a strong move when reading friction.  Also, the new C*(System) versa-max would be a good choice as well which you could easily adjust the surface too.  The versa-max has such a smooth reaction that it should work well on all 4 patterns.  Since you are left handed, there shouldn't be as much transition as the right side which will allow you to play in the same area of the lane longer.  Good luck with the tough decision.

Either solid Nexus and a Misfit.

 

It is hard to pass up such a versatile ball as the Reckless though, ball is money on so many conditions.

Hey guys thanks for the updates so far.  Some background on my preferred game....

 

I'm a Lefty, speed dominant tweener.  I can rev up the  ball but prefer not too.  I prefer to play straight and like the outside  of the lane around 567 more than inside 10 but can play inside if need  be (very direct).  16-17 mph, 30* axis rotation, approx 295-325 rpm  (never really measured).  (think parker bohn but with less speed, bout the same  rev.)

 

I'm leaning towards the Nexxus (i have one  and love it, wouldn't mind another) or the regular nexus solid.  I am  still not certain on the second piece, either a nexus pearl (again have  one and love it, another with a different layout would be great),  versamax, reckless, Karma A+ or misfit.   Both balls whatever I pick will be drilled the same with a smooth reacting drilling for control. 
 

 

Any more thoughts?  I like the idea of going  nexxus/nexus solid and nexus pearl, I can use my speed to make up for  stronger gear and I can throw my nexus pearl on THS now, just worried  about cheetah with that ball but the solid with polish might be fine.   Trying to be careful not to buy a ball that's too weak for this concept  and not get to use it when I can't use my stronger one.  Thanks for the  help....
 

Gotta agree with the other guys here. I think you'd be making a mistake NOT having the Versa-Max in your bag.