Somebody over at prorec.com has said that you don't need to use that switch for SF products because they read smaller block clusters. I have never used it and it has never been a problem in Vegas. Heck, I am getting 60-70 tracks using a 20 gig 7200 IDE audio drive with a 700 mhz. Do you really need more?
This info is for audio only. I don't know how it would effect video.