1) Sata III only provides increase in burst performance for sata iii HDDs sustainded read/writes are NOT improved. You will see almost no differece between a SATA III HDD on Sata III port vs Sata II. SATA III SSDs currently are the only drives that benifit from Sata III. This will change as Hard Disk manuf start to incorporate a small SSD internally (functions like SRT in SB based systems. Segate has already come out (or will be) a 2.5 " HDD with an internal 8 gig SSD.
2) sounds more like a driver problem, than a Bios problem. Check manuf Website for there newest Marvel driver.