[therealfiona]

Depends. Do you care about FLAC vs MP3 quality? Then onboard will likely never be enough despite it being highly unlikely you can tell the difference when the song is ripped from the same audio source. (I can sometimes on my setups at home, but never could in the car)

If you have a decent set of headphones or speakers, grab a soundcard from the jungle site and find out. If you can't tell a difference, return it and keep your money.

It is subjective. Just depends on what is important to you. Pretty much everything has 24bit/96khz capabilities if not 32bit/192khz capabilities these days. IMHO, it comes down to if the opamp on the device is of good enough quality for the device you're driving. You don't want to plug a set of 600ohm headphones into a generic onboard sound device and expect it to sound like it would if you bought a proper DAC+amp setup. It simply doesn't have the power. If the sound device has a line-out, then you only need an amp.