Epia SP
OK here's a technical solution to needing more horsepower to do MPEG4 decoding with VIA. First they have a super small form factor EPIA N coming in April. This will be a super small system, but with an updated memory interface.
They are also doing a mini-ITX version too using a board called the EPIA SP. This is tuned not just for MPEG2, but also MPEG4 and it supports faster memory running at DDR400 rather than DDR266 plus a 1.33GHz processor.
Both are something to wait for. Hexus has a review of the upcoming Tranquil T2 based on the new board as well as the the older MII based system running windows media center 2005 called the T2.e.
The Tranquil by the way like the Hush is fanless.