This is some great info, everyone! To answer your question, Len, yeah,
I'm still here!

I posted the question looking for specs for the perfect PC, so I'd have
something to shoot for. I'm glad to say that I've already met some of
these, some are a little more of a challenge, but not impossible.

For instance, I decided early on to use the EPIA mini-ITX platform.
Right now, I'm focused on the MII120000, but different boards can be
used for different purposes.

A few questions/follow ups:

- 6 serial ports is a little tough to do with current PC platforms,
most users don't use them (although we all know that we do!). Not
impossible by any means though.

- a 12V USB hub shouldn't be difficult to find, though I haven't really
looked, it's more of a peripheral. Definitely worth looking into as an
accessory though. A panel-style mount is an interesting idea. You
want to mount it right to the bulkhead in your nav station?

- Len, you mentioned that you want "remote connectors" for the USB.
The USB has to connect to the box somewhere. Do you want to move the
back-panel connectors to the front, or the side or something? To
perhaps limit the need to access the back?

- Also, Len, why an external hard drive? Do you mean an extra external
drive with one built in? This gives me the idea of modularizing as
much as possible. We could get this size down really small if
everything is an add-on (Optical drive, USB hub, storage drives,
etc...).

- as far as entertainment/music, my thought has been that this PC can
be your entertainment center as well. Just run speakers to the
cockpit, or wherever and just play mp3s straight from the PC. DVD just
depends on the optical drive, TV will probably require another card.

- it seems that there is a lot interest in video options. Let me tell
you about something I did for a customer in the past. He had a
standard LCD screen at his nav station, and an all-weather LCD at his
helm. He wanted to see the same image on both screens, but they were
at different resolutions (the helm LCD only supported 800x600).

All we did was use a VGA splitter cable, and I installed a couple of
batch scripts on the desktop to quickly change resolutions depending on
which monitor he was using at the time. I haven't gotten into selling
monitors (yet), but his helm monitor had a USB port, so he could easily
connect a trackball when he needed it. The whole 2 monitor solution,
costs about $12 (not including the monitors or trackball, of course).

I also see some interest in LVDS connections. I looked into that
because I know a competitor is offering an LVDS all weather display,
but from what I can tell, he's the only one in the PC industry doing so
(please correct me if you've seen more than one). The EPIA LVDS module
provides a good connection for a laptop LCD screen (as in an all in one
PC), but not an external monitor. There needs to be another cable to
bring that connection to the outside of the PC case, but there isn't
really a standard for external LVDS (that I can find). The desktop
industry seems to have gone the way of DVI for connecting an external
monitor to a digital video source.

Thanks for everyone's input! Keep it coming!

Eric