The "Home Media Centre" concept can be summarized as turning your television set into an entertainment centre, i.e. migrating what you usually do on your computer to your TV; such as watching mpeg videos, photos, DVDs, YouTube, IPTV, internet radio and various other medias stored on a hard-drive or over the internet.
Over the past couple of weeks, I have managed to setup my own low-cost media center for around $130, with most of the cost going to a brand-new wireless router as you shall read.
A couple of months ago, I bought a pre-owned Microsoft XBox (the original one) for $50 and installed XBox Media Centre (XBMC http://xbmc.org/) onto it. I followed one of the softmod installation guides found on the internet, which was pretty straight-forward. I completed the whole process at home without needing to bring the console to a shop and modify its hardware. The installation process basically utilizes another desktop PC as a platform to load XBMC OS onto XBox's harddrive (through IDE cable) as though it were its own, and then it's done.
Then I connect the media centre to the internet. My ADSL modem is located quite far away from the television set. As I have previously setup wireless internet, I decided to install dd-wrt (v24-sp2) onto D-Link's DIR 600, set it to "repeater bridge" mode and connect to the xbox with Ethernet cable. As a side note, the wireless router cost me more than $70 but supports only 802.11g...
In terms of functionalities, the original Xbox has component cables (Yellow/Green/White) supporting SD (standard definition) video - good enough for watching DVDs.
The whole setup is now sitting in my living room. I use it mostly for listening to internet radio provided by my ISP and occasionally watching DVD. I have also downloaded a YouTube script so I can watch YouTube on TV... although the Xbox seems to struggle with High-Definition videos. Nonetheless, it is still good value for $50.
As a side note, I also purchased Xbox's DVD kit over Ebay, giving me a remote controller to this media centre. There are some photos of this setup in the "photo gallery"...