SiSandra.
Don't be fooled by a RAID 0, benchmarks will tell you you're getting about double the transfer rate, but in real world applications, the difference isn't nearly as noticable as benchmarks will lead one to believe.
SATAII seems to be the best of the best right now.
Also, hard drives are not measured in hertz/megahertz/gigahertz as they do not perform instructions.