No single mechanical harddisk can use 100% of SATA II 3Gb/s bandwidth, thus with SATA III 6Gb/s, you won't get any performance increase AT ALL.
+1 to that.
It's unfortunate though how many people don't realize these facts and go ahead with hardware purchases thinking it will yield a good difference.
According to NewEgg the Asus P6X58D supports Sata 6.0Gbps
Newegg.com - ASUS P6X58D-E LGA 1366 Intel X58 SATA 6Gb/s USB 3.0 ATX Intel Motherboard
Although, as stated above, the drive simply won't perform any better since it wasn't even maxing out the SATA 3.0Gbps interface.