newb, in car pc, avoiding disaster?

Hello, I am finally going to be able to start installation of all my bought components. My goal is to have a full desktop pc in the car to handle every form of entertainment I could possibly desire while on the move and/or relaxing in some beach.

Question1:  Can I use solid wire instead of stranded for small electronics such as a PC shutoff and power on module. I bought this module some time ago and have never connected it. It is suppose to handle the powering on and shut off of a pc while in a vehicle. it has timers and options to send signals to the pc to shut it down when car is turned off. The wiring that came with it is small maybe 20 gauge. I looked around and wire is pretty expensive so can i go to Home depot and buy a 50ft cable used to handle sprinkler systems and just solder thos solid 18gauge wires to the existsing stranded 20 gauge. The 18 gauge can handle low voltage and low amps up to 50 amps i think. I doubt that such amperage will be used in sending and recieving signals to the module but that is why I am asking here to the more knowledgeable. Can I use this setup and not fry anything if done correctly?

Question Two: Should I buy a second smaller AGM battery to handle only the pc power? I was going to use a power inverter to convert the power to ac and then the pc power supply will convert it back to dc (pointless and effeciency loss) is this the only way? Is there something that I can use or make to use the Car 12volt to power the pc? If so do I need to use a seperate smaller battery than the Odyssey battery I bought for crankig and continous use for vehicle operation. I know pc's need clean power, can I make this happen without dropping a fortune or frying the pc?

I will leave with those question out there, please please help me decide what to do. Space is limited and money too, lol. A PC power supply able to handle the pc comfortably will be about 80$ plus another 80-120 for the convertor. I'd say a DIY that will give me some saftey and reliablility would be very useful. Thank you for your time and any advice you may provide.

The problem with this is that they are not strong enough to power the components I have. I Have a Biostar MB with a dual core athlon 5600+ , dvdrw drive, will run about 3 to 4 usb periphreals a single but possible dual video card setup later on for now a single. All in all in the power calculator in th Antec website I would need around 555 watts with the dual card setup so I would want to aim for a 600 to 680 watt PSU just to be safe for efficiency and upgradeability purposes. So I woudl need a 680watt PSU to power all the components adequately. Can I make one of these power filters to give clean power to the pc?

What about the wire? Can i use solid wire instead of stranded? Is there a problem with current, amperage, voltage, etc... Since I'm a newb I have to apologize for any obvious questions I may be asking. Thanks again for your advice.  

There isn't a problem with current, amperage, voltage, etc from an electrical standpoint, but there is a reliability issue - solid core wire is meant for places where there are no vibrations and no moving parts (like inside the walls of stationary buildings).  The single core won't have a high probability of surviving in a moving car.  If you think wire is expensive you either don't have deep enough pockets for a project like this or you are looking in the wrong place.  Check out www.delcity.net for cheap wire or places like Parts Express ( www.PartsExpress.com).  Speaker wire would work great for signal  wiring.

The computer you spec'd out is, in my opinion, overkill for an automotive environment.  I would try to minimize power requirement so that you can back in to a automotive grade power supply - you will have better luck in the long run using automotive grade parts instead of desktop computer parts (another part designed for a stationary life). 

Good luck!