The ULTIMATE PC sound system (official thread)

Post amp I'd suggest.

@dennispeeters27 I'll add to what Matt said here regarding the current drain. It's a good idea to know the drain in advance so you can pick the correct supply.

Current and voltage confuse a lot of people so I might do a blog post about it another time.

I assume you have a DVM  - multimeter - of some sort (they're cheap enough to get a small one these days if not). You should set it for current and put in SERIES with one of the supply lines, starting with the most the meter can handle (cheap ones might not be properly fused) and work down until you know how much current the device is demanding. 

With an audio system the load current (the current the device is demanding) increases with volume. Modern systems often use Class D amps which are highly efficient and can produce quite a bit of power from a tiny IC.

Anyway, once you can safely monitor the draw, you can push the volume and see what happens.

The alternative (which I don't recommend) is to use the voltage setting and look at the supply voltage as the load (volume) is increased. The instant you see a drop in input voltage - even a fraction of a volt, you know you're pushing the supply too hard. 

The caveat here is that unregulated supplies can catch you out because they produce very high potential voltages until they are under load and things settle down. Most modern electronics shouldn't be connected to these things as that sudden voltage might just be enough to jigger then. Besides which, regulators are cheap and easy to fit so there's really no excuses any more.