Does this power supply fit well in this new system to be built?

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.

judging by the hardware, get a seasonic m12II 520w. it is on sale at newegg for 59.99. very high quality and semi-modular too

I see. But what if in a future I buy a graphics card such as the ATI RAEDON HD 6870?

A quality 500w psu like TheBigTroll listed will be ok for a 6870.
http://www.amd.com/us/products/desktop/graphics/amd-rad...
Or, a GTX670, for that matter.

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?

the cpu inside is worse than a pentium g630just saying. it will get you through some very basic tasks though