unless you're attaching some really crazy stuff to it, (and given how slow an epia 800 is, i don't think attaching much power-hungry stuff would work very well anyway) there's no reason an M1-ATX wouldn't be enough for it. the epias (the 800 especially) use so little power it's ridiculous.
But don't take it from me! here's a quote from a real, live newbie:
Originally posted by Viscouse
I am learning buttloads just by searching on this forum. I've learned 2 big things so far: 1-it's been done before, and 2-if it hasn't, there is a way to do it.
I have a Via MIIK1000, laptop HD, USB GPS, PCMCIIA sound card, IR reciever for steering wheel mounted remote, and a firewire DVD drive that gets it's power from the mobo. All powered off of an M1-ATX. I have never had any problems with it as for as power goes. With just 800MHz you'll be fine with a M1, it's when you get into p4 territory and such that you start having problems
-ZtH01 "It's my belief that my big balls should be held every night"