ASUS CH IV memory can run DDR3-2000MHz (2GBx4) with Thuban , QVL memory vendor : G.Skill, Kingston ,OCZ , Transcend ,..... .
The IMC of AMD Phenom II X6 is better than Phenom II X4 ,

Tomshardware testing 890FX MB comparison of Maximum DRAM data Rate ,
using Phenom II X4 965 Black Edition with Kingston HyperX 2133 CL9 ,
ASUS CH IV is the memory overclocking lead , 4 Modules / DDR3-1928 MHz
Gigabyte 890FXA-UD7 , 4 Modules / DDR3-1790 MHz

For your reference , If you care the memory performance .