Hi Sam,
I use external controllers on all machines, some Smoothstepper, some CSMIO.
The via Pico mobos dont have a PP but the Asus mini ITX I used does, I never actually tried running anything with it but out of interest I tried the driver test and it was the nicest pulse I had seen on any mobo right up to 100KHz. Whether all Atom mobos will be similar I cant say.
Hood