Wow it's almost been 5 months since I posted, here's what happened:

Over Christmas vacation I made everything more permanent and added a few features. Basically I got the M4-ATX and used an old desktop, built a wooden mount for under the seat, painted it black, and mounted the mobo, HDD, and power under the passenger seat.
I finally removed the old head unit and installed a 4 channel 400 watt amp under the driver seat.
I moved the wifi usb adapter to inside the dash for better reception, and I added a OBD II scanner and a joy-con to control my pc with the steering wheel controls. oh and also threw in a cheap back-up cam for kicks.

Everything works great, i'm surprised that the old mechanical HDD is holding up under the abuse of riding in a car without shock-mounting, but that's why i chose such an old HDD that i didn't care if it failed.

Then i kept procrastinating on posting...then I kept having surprises that ate away from my extra play money for my carPC...then i put a crap-load of miles on my car.

So i started doubting that I should keep putting extra goodies in a 2008 car that will soon have 100k miles, and what made up my mind was a racoon that ran out in front of me and ripped off a chunk of my front bumper and the entire fender liner.
The liner is getting replaced, but the bumper is only cosmetic and not worth the money replacing it.

So my xB is now officially my work horse, not a to-be-tricked-out ride that i drive daily.

On the other hand, it will be paid off soon, and I'm going to save up and buy a MR2 Spyder, a fun little mid-engine convertible. Then i'll start back on it, and probably with all new hardware.

I haven't uploaded any more pics, but if anyone wants to see the progress i made since Christmas (or wants to see what a 'coon can do to a bumper) i'll be glad to post them, or answer any questions about my install.

And lets hope I can get this Spyder soon!