Because you do not list your other components, it is impossible to tell. Your cable seems to be OK, but all SATA cables are supposed to handle SATA III bandwidth. The problem may be with the interface between your mobo and the controller card. The controller card can do exchanges with the SSD at SATA III specs, but your bottleneck may be the mobo itself.
If you are running an older mobo you may run into the problem that an added controller card is limited in the bandwidth that it has for throughput to the CPU and otner peripherals. List your mobo and CPU and other conmponents and you can get better advice.
I decided to upgrade the motherboard and return the SSD for now and get another one when the price drops a bit. Will the sata ports on this motherboard get the full read and write speed? http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Also, the computer that I currently have is an HP. If I get the new motherboard and put in the cpu that is currently in the HP, will I be able to overclock or does HP lock the speed on the processor? Do you know of any cheap, but sturdy case to go with the motherboard?