150w is more than you need.
For reference I am running a mini-ITX with the following:
I7 3770S (65w TDP)
8 gigs of ram
Blu ray drive
Keyboard, Mouse, Webcam, BT USB, z-wave USB
All running on a CityNet 150w PicoPSU fed by a 120w AC-DC adapter.
Peak power at the wall as measured by Kill-a-watt meter never ever EVER... gets close to 100w - in fact I don't think I have ever seen it exceed 80w at the wall.
Intel Desktop utilities show steady voltage, a good indication that the PSU is not overloaded.