Or when you are annoyed by a shitty soundcard in your business notebook, get a Behringer external DAC/soundcard for $29 ( http://nwavguy.blogspot.de/2011/02/behringer-uca202-review.h... )
If I'm that deaf to the differences between these two sources, I'm curious if people think the UCA202 will change my life?
The other big issue is distortion/nonlinearity. This is much less of an issue than the noise floor, but can still be noticeable on cheap DACs.
It's likely that you can do a lot better than a $5 DAC on both of these factors.
Also depends on how "hard" your audio equipment to feed. You don't go hanging big speakers directly to your PC kind-of-thing.