I've recently caught bass fever and now my home setup just won't due. This being said I have a spare 600 watt amp and was planning to hook up a sub on my home system. I looked into modifying a computer psu to power the car amp over other solutions simply because I build computers as well and have a few laying around. The only thing I'm unsure of is this... am I going to need a power supply over 600 watts to power the amp? I don't plan on maxing it out but even if I were to I wasn't sure if I just needed any old 12 volt rail considering thats all a car battery is.

If it was me, I'd buy a plate amp or home theater type amp, something that already runs on 120v (wall socket).

It's possible to do what you want, but it's going to be somewhat jerry-rigged and what not.

Is this going in your house? Or your car?

I am planning on setting this up in my house, and I realize that it is a little bit rigged, but I'm trying to achieve this with little to no cost, since I have PSU's, an amp and a sub. I just wanted to get everything straight considering the watts before I go hacking and soldering.

I've done that, it's hard to harness all of the power from the PSU and get the amps that you're wanting.

The PSU will just cut off and die if you pull too much power from it

But I went from a 300 watt one to a 600 watt one, made a huge difference!