There is no such thing as Sata 6 , there is sata 1, sata 2 and sata 3 . What you are referring to , I assume is the maximum supported throughput of SATA 3 , which is 6.0Gbps
Most Full Size 990/970 chipset AM3+ ATX boards will have Sata V 3 . There are not many micro AM3+ mATX boards that have Sata v 3