For the CPU I thougt that the 2100T wouldn't heat up a lot and thus a fanless cooler was good.
Sure, it's possible. But I don't see the point. If you're going to use more than one fan, in principle it would be more efficient to put one directly on the CPU heatsink.
The 2100T is underpowered compared to most current desktop CPU but it's no Atom. It'll heat up at load and you'll need a more substantial heatsink if you want to keep noise low.
I don't think there's much point in using all three case fans by the way.
And I don't know how noisy the stock fans are. Maybe you ought to buy a good case fan separately.
So I should choose a heatsink with fan, and thus there is no need for a T-serie cpu, so I can take the 2100, I'm right ?
The T-series seems to have a small efficiency advantage relative to the regular version. But yeah, the 2100 or even a more powerful CPU would be fine with a more substantial heatsink.
If you want an expensive PSU, the 550W Superflower/Kingwin Platinum is technically the best. The X560 recommended above might be better value or not (I don't know). But the X400 is for sure not very good value at the prices I've seen.