ITX boards can't fit the phases and the amount of FETs needed to reliably push a processor that outputs 125W TDP.
The chances are your motherboard is throttling back the power to your cpu causing bottle necking.
Yeah, I think this is happening. ASUS board so standard feature.
You could remove this problem with a processor undervolt (and underclock as necessary).
Socket FM2/Trinity APU will serve a much better platform for AMD on ITX. The Piledriver cores in the APUs are far more power efficient and they should provide comparable performance to Phenom II. It'll come out shortly, just wait for it.