The m5a78l-m plus/USB has the USB 3 connector on the bottom. And yup it can support 2 USB 3 ports
I've got the connector on this but one is USB 3 the other USB 2 on the front of the case
I dont think any mobos have 2 USB 3 headers. Only 1. There's not enough room for 2 or more.
The rest of the USB 3 ports will be on the back of the mobo