Small Linux boxes?

[Kevin]

I am looking for some hardware suggestions for my next project.

BACKGROUND
I have a Squid/Dansguardian setup for my kids that has worked flawlessly for
several years.  It ran on Gentoo and now it runs on Debian.  It includes a
web-based Apache/PHP front-end that I wrote myself.

My friends and family (non-geeks) with youngsters are interested in
duplicating my setup.  I would like to take this evolved collection of hacks
and package it into a single image that could be dropped onto a similar
dual-nic box.


SUGGESTIONS?
Here's where I need suggestions.  I'm not interested in family tech support
on a bunch of old clunker PC's (like my setup).  I would rather package the
software "solution" onto a small headless Linux box they can just plug into
their cable modems.  I have priced out a mini-ITX box with dual-nics and VIA
EPIA processor.  I'm approaching the $500+ range.  A bit too pricey for my
friends/family.  

Any other suggestions?  Or, maybe mini-ITX is the way to go and you can
suggest a cost-effective wholesaler or something?

...Kevin