One more thing to consider; there have been a couple of very good threads the past couple days about "heavy oil hype"...
People are buying stronger and stronger balls looking for that one ball that'll have them shooting the honor scores. However, the stronger equipment is not reacting the way you hope they will. Why? Because, there's just not as much oil on your THS as you may be thinking. Milder, more moderately-priced equipment many times reacts much more on THS's (then the state of the art...) because they're not burning up in the heads and midlane. The milder balls conserve more energy and will have more pop in the backend; if they're too squirrelly, then dull the surface a little till you get the desired reaction.
So when your proshop guy tries to steer you towards a milder-reacting ball than what you think you need, that's the time to have him explain his reasoning; use his experience! He knows the THS at your house and have him watch you; he'll know what will match up better for you and probably can save you some money too! If you don't trust him, find one that is respected in your area.
While I'm at it, you should be able to use a ball - one ball - for your entire league night. Learn to make 1-1, 2-1, adjustments as the lanes transition. Now if you chose the wrong ball to start out and you figure that out, then change, but planning to change balls as a first adjustment can get expensive!
Dave