Im currently running an eGreat M34a for my media centre, which has been fine but ever since the nvidia ion was announced last year i've wanted to build one.
The Asrock being dual core atom 330 handles high def video fine, seems to keep above 24 fps which is ok doing PAL.
There's a youtube video comparing the Asrock ION and the Acer ION (Revo) and the Acer drops frames on 1080p video, as low as 18 fps, which is unacceptable for media centre and high def video playback. There is also an acer revo nettop based on nvidia ion, but it's single core atom.
I found some on eBay for AU $374.45 +AU $62.42 postage, excluding RAM and HDD.