SSDs are the only thing that will max out an SATA 2 connection and probably an SATA 3 connection in the near future.
If you're using an older system then just stick with SATA 2 for a boot SSD, it will be plenty fast.
The other options are to get a SATA 3 PCI-Express card or a PCI-Express SSD.
Wrong forum category but probably not. SATA 6.0 Gbps controller chips debuted after motherboard manufacturers launched their final P45 motherboard designs/models/revisions.