I know that some people have used a picoPSU (which involves changing the socket at the back) but I wondered if anyone had tried one of these gadgets? With a figure 8 power connector, and a 3.3v voltage regulator added to a fork off the 5v line I think it's just enough to power the DC. Contemplating trying it if my DC develops the resetting fault again!
18W sounds a bit low to me. I have no idea how much power the Dreamcast is actually pulling though. Assuming you have already looked into that, I don't see why it shouldn't work.
Dreamcast needs around 22W of power so that psu probably won't cut it. Image by Taijigamer2 posted Sep 26, 2015 at 9:31 PM Here is my dreamcast hooked up to a modified ATX psu in a multibox mod. Not very space saving