Alrighty, everyone is going to tell you to use google and search for your answers. I'd suggest that in addition to what I'm going to throw out here, I don't have time to list everything and explain it all too.
You need everything for a (mostly) standard computer. Alot of people will suggest a small form factor, low power board like the VIA M10000, laptop hard drive and CD drive because they have built in shock protection, everything else is up to you GPS, etc.
Power is the big question on everyone's mind, alot of people will tell you to use an Opus because they are the best, don't take that advice lightly. Other options are power inverters or like you mentioned the PW-70a and ITPS thing. The PW-70 is for very low power applications, like the ones sold on
www.mini-box.com. If an opus is out of your budget completely I would suggest a setup with an inverter and an ITPS type device.
Read all the threads though, read them often. This is the best way to answer your questions.