As far as I know, the WD Velociraptor at 10K rpm is the highest rotational speed you can get in a SATA drive. But, there isn't any reason I'm aware of why you couldn't use a SAS drive with any of the adapters you've linked to. All the same, I'm curious about what prompted the thread, if you don't mind sharing.
More speed of course. I own the Velociraptor and it is fast, but not as fast as a 15k drive. I have read that the motherboard has to be able to communicate with an SAS host in order to use a SAS hard drive and thus simply swapping the connections wont work. Any info on that?
Sorry, this isn't something I've tried to do. A couple of years ago when I wanted more drive performance I moved to a SSD as my primary drive and a 1 TB WD Black as my data drive, which also has some of my less frequently used software installed there. I've also done some builds with similar drive specs, and I've been very happy with the results.
Over the years I've done RAID 0 arrays with Raptors and Cheetahs, and reliability issues aside, the performance doesn't even come close to SSD performance. So, have you considered any SSDs at all? Especially if you run Win7 or 8, a solid state drive/HDD combo really kicks ass.