I am not familiar with MTEK, but it looks to me from brief research, to be a cheap power supply that is best avoided.
Stick with known good quality psu's like Antec, Corsair, Seasonic, XFX, PC P&C.
Without a discrete graphics card, your power requirements are minimal. 300w should do it. There is nothing wrong with overprovisioning a bit, since the psu will only use the power it needs. A 400-450w unit will not be any more expensive.
But, the reason you buy a llano is because of the superior integrated graphics. The cpu is not as good as intel if you will use a discrete graphics card. Perhaps you should reconsider your build strategy.
What is your budget, and what is the primary use for this PC?