hmmm this is weird, i looked up both dx and dg again, and both being compared and guess what they said...
dx vs onboard - dx is waaaay better than onboard, just grab it and you wont regret it.
dg vs onboard - dg will sound better than onboard and will be a good upgrade over it, though the difference in quality wouldn't be big.
dx vs dg - dg sounds better than dx.
i luled at this part.
edit: also i still cant see the reason for needing an amp, if the soundcard can drive it loud enough for me without any sort of distortion wouldn't that be enough? an amplifier is basically, well, an amplifier.
also people claiming that amps makes it sound much better, as if enhancing the signal, well wouldn't that mean they're distorting the signal to the sound they'd like? wouldn't an EQ do better?