What is your budget? I recommend only if you run out the SATA ports. And you can buy any one of them.
But if you want to buy that card for your HDD, I recommend don't buy it because most HDDs including the WD Raptor or seagate SSHD will no have more than 200MB/s read/write or transfer rate. And the SATAII has 3 Gbit/s - 300 MB/s transfer rate, only the SATAIII SSD will have that speed (SATAIII - 6 Gbit/s - 600 MB/s). But if you want to but the card for SSD, then the good add on card will be more than you can buy the new MB+ CPU.