You have sata III port - Sata II will NOT yield the Sequencial scores your screen shot shows. If the people suggesting that as a problem had look....
inzone is correct along with C19 comment about the amd driver - If you notice almost ALL test beds for SSDs use Intel chipsets - Two reasons 1) mainly intel has 85% market share and 2) Intel chipset/driver performs slightly better.
NOTE: double check your SSD firmware and make sure it is not a pre-release version. Ref: http://www.anandtech.com/show/6483/update-on-samsung-ssd-840840-pro-failures
And a review of 840 250 gig: http://www.anandtech.com/show/6337/samsung-ssd-840-250gb-review