Well, after much deliberation on mac vs PC, screen size, head unit or no head unit, software options, etc - the parts were purchased and the install completed.
What went in:
Used Xenarc TSV-700 5-wire touch screen_______$270.00 (ebay)
BU-353 GPS Antenna_________________________$75.00
Carnetix p-2140 (from mp3carstore) ____________$135.00
Aluminum WRX bolt in kit (mp3carstore) _________$130.00
USB cables, monitor cables and connectors,
wires, switches, etc _________________________$150.00ish
My Casio V2000 Laptop_______________________FREE
3 All nighters installing --The fun part___________FREE
TOTAL:
$760.00
I went with centrafuse as my front end and so far have been pretty satisfied.
First off, the ride:

My 2002 Subaru Impreza WRX Wagon
After I decided that I was going to use my laptop instead of a dedicated carputer, I had to devise a way to make it east to remove (and re-install) if I wanted to bring it with me someplace other than the car. I decided to mount it under the trunk floor/lid to the storage compartment above the spare tire. I still wanted to be able to have full functionality of the trunk space, so keeping it small was essential. I decided to go with aluminum plate, bent and mounted to a piano hinge so I could open the trunk and troubleshoot with the keyboard open if necessary (turned out to be quite useful):

The floor of the trunk
You can see the P-2140 at the bottom left corner of that last picture. This sweet little box made my carnetix was just what I was looking for. Its a dual output regulated power supply and has nearly infinite options for applications. It connects via USB to the computer and you can change all the start up/shut down parameters very quickly and easily. Its also really nice to get a visual display of the input voltage, output voltage and wattage, temperature, etc. I'm very impressed with it so far and haven't had any problems.
Backtracking a little bit...this was the setup before the install, making sure everything worked the way it was supposed to (really the hardest part of the whole ordeal)

The Setup
Getting wires to the power button on the laptop was tricky and time consuming, but once it was soldered and epoxy'd into place, the power supply will boot and shut down the computer with the turn of the Key

The quick to plug in/take out power button mod
After I got all that working on the kitchen table I was ready to run wires in the car (running audio and video down the drivers side rocker panels and power/ignition down the passenger's side - and I haven't had any interference to date)
The trunk wired up and computer installed:
The final product, hidden away...with no loss of functional space:
Next was installing the screen. This took a little bit of custom work because I purchased, as shown above, the Xenarc 700 TSV. Its slightly larger than the lilliput screen but I had hoped that it would fit in the WRX specific aluminum case that this site sold. Well, it arrived in the mail and when i checked for fit, it was no good. So, with a little fabrication, trimming, hot gluing, and more fitment tests than I care to recall...I arrived at the finished product:

The old and new, side by side.

This took a little convincing too because the xenarc buttons are not on a separate micro board. They're mounted on a board that runs the whole height of the unit, so the only way to get it to fit was to mount the panel at an angle using a piece of bent aluminum with 3M dual stickyback holding it on (and so far so good).
So the 2nd all nighter begins...

Notice the new head unit under the seat...more to come on that later
http://image16.webshots.com/16/8/91/...tions/FullSize
Just under the AC controls is a CB radio...the next pic shows it covered up by the new faceplate/radio controls, but it still works, you just have to reach up/behind the faceplate to turn it on, but I don't use it very often, so its all good.
http://image59.webshots.com/759/5/58...tions/FullSize
The Pioneer head unit matches the instrument cluster perfectly, even at night with the green accents

Also, I didn't want to trim the actual bezel that fits over the screen, mainly because I'm not very good with molding plastic and I didnt want to paint it, so I outlined the screen with electrical tape (I know, the not the most professional approach, but it works and looks way better than jagged or poorly molded/pained plastic)