--------------------------That psu is a dc to dc psu. You need a psu that can convert the alternative current from your wall socket to direct current used by your pc. I would suggest looking the sliverstone itx comptable psu's if you need aomthing small.
---------------h--The PicoPSU itself is DC-DC, you then use an AC-DC 12v adaptor. All you're really doing is moving the PSU outside the case.
A 150W PSU would be tight for that setup but should work. I'd overspec the AC-DC adaptor though, there is a 192W one available, and for the marginal increase in cost I'd probably go for the 160W picoPSU.
In fact, doing it myself, I'd probably do a T series (35W) CPU and reduce the power usage.