As big as it is (and it is a big PC power supply), this is still a
switching power supply. This would still be a poor choice of supply for powering something meant to be in a car. It simply cannot supply the kind of current a car audio amplifier will be demanding constantly.
What you would need is something more like this or even larger if you can find it:
http://store.yahoo.com/allcable/alsmpowsup7.htmlBasically, beware of any power supply that does not include a hefty (meaning very large and very heavy) transformer. If you have a surround sound receiver that puts out 75 to 100 watts per channel, take a look through the vent grill on the case. Chances are, you'll find one of these humongus transformers I am talking about. Anything without a large transormer is probably a switching power supply that can only deliver the rated output for very short bursts. A PC power supply falls into this catagory.
I have found that for the most part, making things designed for a car work without the car is not always a fruitful endeavour. Speakers are the exception as though they are 4 ohms and the standard home speakers are 8 ohms, most current day, higher technology amplifiers are capable of driving the smaller loads (ever see a car amp ad that says "2 ohm stable"?).
Hope this helps
Bumble