Anandtech did publish a 1st impression of the anounced Eee Box from ASUS & dissected this small desktop PC.
The Eee Box Anandtech received features a 1.6GHz Intel Atom processor paired with an Intel 945G chipset, 1GB of DDR2-667 memory & a 160GB Seagate Momentus 5400.4 2.5" SATA HDD. The Eee Box features Gigabit Ethernet & 802.11n wireless & Bluetooth.
The Eee Box had Windows XP running & according to the reviewer "the Atom processor is surprisingly quick"
Although the Eee Box is fast enough to decode DivX/Xvid, it doesn't have enough horsepower to do full 1080p H.264. At a low bitrate of 720p H.264 it is possible to decode video files, but the CPU utilization gets at around 90%. So you could use it as a mediacenter, but only at lower resolutions.