Check out http://www.stangnet.com/Tech-Article...Head-Unit.html
This should be helpful!
I think you could do this without too much trouble, actually. You need to find a harness that goes from the square amp harness to RCA. I have seen them out there, but I don't know where to get them. If you can't find one, you can solder RCA ends onto a harness like the Metra 70-5511. Then just run RCA cables back to your carputer, use an RCA-mini adapter and your set. Be sure to turn the factory amp on by sending 12V to the blue/white wire in the gray aftermarket power harness. I don't know how it would sound, but it would work. Good luck.
the metra one is no good. get the scosche adapter from crutchfield.com
Holy crap, thanks for the awesome responses, guys! I knew there was a way! I already ordered a ton of different components, but I guess they're going in my porsche
1995 Ford Mustang Convertible
DSATX | Shuttle XPC SN41G2Bv2 | 619GL-70NP | CF 1.6 (which is still unusable in the car!)
It looks like your Shuttle PC has the same sound output as my VIA M10000 mini-itx motherboard so we should be going through the same learning curve. I ordered the METRA 70-5519 Harness Friday (after finding that article on stangnet) and I'm fabricating the CarPC case for my 2001 Mustang right now. The dash is all ripped apart and I feel you pain! I sure hope we don't have to go buy new amps! The MACH460 amps seem to have plenty of punch. I really like what Specimen did on 94 Mustang GT and plan on following his design.
I know you've been given alot of mach 460 info already, but take a look at what I have on my personal site (link in sig). You might find something useful there. I have schematics/diagrams/pics. I actually took my front amp out and added an aftermarket headunit while maintaining, if not improving, the sound. I'm still utilizing the rear amps. peace...
www.crutchfield.com has a huge amount of info on this stuff.
Although I would like to have an aftermarket amp and speakers, for now I am going to use the stock Mach 460 amp until I get some more cash.