So long as the hardware supports wake-on-LAN (WOL, for use with the media extenders), the rest is just about all up to the software.

EDIT: Mmm.. I do keep forgetting that, on MSWin, functionality of hardware is frequently restricted by software and drivers, and the only way to gain features is often to buy newer hardware so as to gain access to the improved drivers/software. Ugh, great way to make money, but disrespectful of one's user base.

Pity that MythTV is still a major pain to set up initially, because it handles all of that stuff with aplomb.

SageTV claims to support shutdown and autowake, in conjunction with Windows power management. But I never did get a straight answer from anyone about the same stuff with SageTV on Linux.

-ml