It seems a great way of cooling your machine, but I can only find a couple of BTX fans, couple of cases, and have only seen one micro-btx mobo.
For those of you who don't know it, the processor is places on the mobo towards the front of the case and the cpu fan draws air in from the front, over the cpu and blows it towards the graphics card which is in a position to get full effect from the airflow.
Instead of it fitting to the left side of the case (like ATX), it goes on the right. The graphics card is upside down so the gpu is pointing up.
You can have a look at the form here:
Here's a pic of a btx mobo: