I just came across the Neuros LINK. It is a media player that is built around a full PC and full OS. I guess that makes it an off-the-shelf HTPC.
are the technical specs.
It is an AMD 780g with an ATI Radeon HD 3200 video card, and a low power CPU, in an HTPC style case.
It has 11g wifi, an eSATA port, a wireless keyboard/mouse combo.
It seems to come with enough storage for the OS, but no space for storing content.
It comes with a media player version of the Ubuntu 8.10 Linux OS, which I think is a very good thing but some people might not like this.
It is too new for there to be reviews so it would be hard to say whether it is quiet. Note that the software is still under development and this is considered a beta product.
The price - US$300 - is much less then it would cost me to assemble and build these components myself, but I doubt it is available in Canada so it would have to be shipped from the US.