there would be no benefit in using the new sata as a high storage HDD can not exceed the banwith of the current version. Also full 3.0 speeds will not ever exceed current sata speeds and the max speed of the buss will not be supported until the end of next year.

Lastly m/b raid controllers are always very slow compared to a dedicated board. When the HDD prices fall I am going to buy a 8port raid card and run RAID 6 on 8 drives. This way I can get really good performance and stability along with high storage. However this plan is based on 2tb costs dropping in a few months or so.

Also they have nothing to due with gpu speeds...

If you use onboard and you have a very large array you do cut into your cpu and ram a lot but on a system like mine there are extra resources. However even if you do have the extra resources a dedicated express card is always faster.