AFAIK, there are no SATA II Raptors, there's no need for SATA II at all right now really anyway, at least for the typical gamer. It's premature IMO. Raptor's are only needed really for gaming and intensive programs, so if your not doing that steer away from them.
Also, a 74Gb Raptor is $150, 2x36.7Gb Raptoprs is $200. If RAID is faster, and you want to pay the extra $50 go ahead. Personally, I don't think that the extra $50, slight increase in performance, and extra cable dangling in your case is worth it.