I've seen nothing to demonstrate that the crossdrilled rotors help with any kind of reliability. The rotors need all the metal they can get; I believe that crossdrilling reduces heatsink area and at best, provides no benefit. It's possible that they could increase the tendency of these rotors to warp.
On cars I've worked on with repeat rotor warping problems, two things work to solve the problem:
1) Use Volvo rotors. If nothing else, you get a 1-year warranty. My second choice would be ATE's.
2) Replace the cone bushings in the front stays. They're cheap and it's not hard to replace them yourself.

They can be difficult cars to prevent this problem - YMMV.
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Rob Bareiss, New London, CT 86 244, 87 244, 88 744