On previous discussion DACs vs onboard; it's not just about the chip, there is an amplifier and analog circuitry. The baseline price for good retail USB DAC one channel (stereo) is about 50e. The price of chip itself is about few euros at volume, which is a lot more pricey than the DAC part of the average mobo soundcard which just has to be sub dollar considering $100 retail mobos have them. Indeed, if you take a look at interfaces utilizing stereo DAC and some additions, you'll come to a baseline price of about 100 euros, for example PiSound which has a Burr Brown with MIDI, microphone input, and two pots.
It would be absurd to claim that a mainboard that costs the same price as stereo interface has the same quality interface on board, and it's also multichannel.
Quality headphones are in audio world what gaming laptops are in gaming world. You pay for the ergonomics, not for the performance. Onboard analog circuitry is just not good enough to drive a proper speaker system. For me it is appropriate for home Hi-Fi tops, and only if you have good DAC on the receiver side so you can just use digital out from the computer. But that still counts as using (and paying for) separate DAC.