Definitely get the magnet 'mod' for the diverter. The powerball is in play maybe 5% of the time. With the magnet I went from a fail diverter drop about 50% down to under 5%. Still happens occasionally but it's the exception now, not the rule. Much less frustrating.
Really with the powerball, how often does it end up in the diverter? And of those occurrences, how many fails? What I'm saying is don't pass on the magnet because it has no effect in PB.
Here's the one I got http://pinballpro.net/shop/twilight-zone-diverter-magnet-tz-dm/