Thanks - I'll have a look at all the Aopen boards.
I think I've hit a major stumbling block, though. It seems none of the cheaper boards (especially mATX) offer underclocking as an option. Only the more expensive enthusiast-overclocker boards have them.
For instance, this is the best one I've found far (£78):
http://tw.giga-byte.com/MotherBoard/Pro ... 20Pro2.htm
The manual implicitly states the Vcore range can be set from 0.8375 to 1.7600 - which is great. But, none of the 8IPE1000 mATX boards have the option, despite only being slightly cheaper (£63-£74).
To tell the truth, I'm not sure how reliable this undervolting/underclocking business will be. The idea is to reduce wattage heat output. I guess the P4 could just run stock with the Heatlane Zen and the first cheap Gigabyte board I mentioned.
It's starting to make less financial sense, if the board costs £80, needs a £14 ZM47J, and a £26 7000 GFX card (total £120). I could buy an A64-2800+ for that price, and splash out on an another K8V Deluxe for £75 to let that automatically undervolt to 1.275 and underclock to 800MHz for me...
It's not easy, this silent PC lark - is it?