Thanks everyone for the input...looks like I'm going pico.
Fair warning - the 150W brick that comes with the 150XT kit is huge! I built a very similar system to yours:
Asrock Z68 Mini ITX
(No optical drive though)
and it only drew 60-70W max.
I ended up buying the 102W brick and using the barrel style plug - the 4-pin DIN connection required by the 150W brick would've meant I had to hack up my case to make it fit, where I already had a hole for the 5mm barrel plug.