Do I need a sound card or DAC?

Audiocards are DACs by themselves - they convert digital signal into analog audio. I would rather ask your question differently:
1. "Would I get better sound if I connect these headphones to an external USB audio card"?
2. "Would I get better sound if I use headphones amp in addition of / instead of above card"?

For music a DAC is usually better
1. The extra processing that gamerk316 mentions is usually not good for the audio quality.
2. Most soundcards use multi-channel DACs. A music DAC would have 2 channel only DACs. Some will use at least one DAC per channel for more accuracy.
3. Some DACs have better headphone amps built in than soundcards.
4. An external DAC is outside the noisy RF environment of a PC case.
You do want high quality files to take advantage of the improvements a DAC can give you.

Can I ask a quick question on this thread. Would using a headphone amp on a pc still be better than the audio card alone...I understand a DAC would be best.

Either Sony MDR-V6 or ATH-M50x will be the headphones.

A soundcard with a dedicated headphone amp will usually have higher quality DACs then the multi-channel outputs. Speaking from experience, I'm quite happy with my Xonar Xense + ATH-M50 (non-x).

That makes sense, I'll definitely look into that as well...in fact my audio card at home might already have that.

Specifically what I was asking about though was I'm looking at a deal on amazon for some ATH-m50x that come bundled with a Fiio A3 AMP. This will undoubtedly make my smartphone sound better but do you think (in general) it would help a PC (if it has a regular soundcard/integrated sound card like my work computer) with something like this setup:
3.5mm line out on the back of the PC (not the front headphone jack)-->AMP-->headphones?

Ben

PS - edit...So my home desktop has the ASUS Z170 Sabertooth Mark I board which has on it a Realtek® ALC1150 chip. I'm curious what you think. It is an integrated audio chip but does have an independent dedicated 2-channel 115/110dB SNR DAC for the front panel headphone port. Or are all integrated audio chips always inferior because of their proximity and direct attachment to the main board and power hungry CPU? Will a PCI audio card always be better?

Or if you are going to buy anything is it just better to get an external USB DAC that will physically remove it from the PC tower case (and extra noise)? The ASUS Essence STX II seems like a terrific card but it's still inside the housing.

If the headphones are pretty efficient and not a difficult load so it's not clear just how much the external amp alone would help. If it's a good deal and you want the amp for you phone anyway then you could try it.
You have to get out of the case before it makes a difference in terms of noise. Having a separate power supply matters. Isolating noise over a USB connection can improve the sound quality too.

Going 3.5->AMP->headphones really isn't necessary; the DAC will be done by the soundcard and that will drive the overall audio quality. The amp is just going to make the output louder at that point.

Note the M50s really don't require an amp; they get plenty loud on their own. I just use my soundcards headphone amp for simplicity reasons (I'm using the 3.5mm output for other audio connections).

Also, as far as DACs go, remember there's more to quality then just SNR. Realtek chips output reasonably clean audio signals nowadays, but audio quality still suffers, be it from compression or just flat audio reproduction.

Thanks for the replies...sounds like either get a good dedicated sound card or a USB DAC for the PC.

As for the deal, I was thinking about using it on my phone as well. However wouldn't a USB DAC work better there too or would an AMP there still make a nice difference.

Anyone use/have experience with the audioquest dragonfly devices...seem pretty straight forward and simple especiaslly if going to use with both a phone and a PC.

Ben

My only concern with driving an amp from a phones if whether it physically puts out enough power to drive the amp properly. We're talking micro USB here; it doesn't put out nearly as much as USB3 would on a PC.

Could be wrong, but make sure you research before purchasing.

I hadn't thought of that...thank you and I will look into it.

Last question about this then...if I got the Dragonfly Red because it will work with my PC straight up and then used it on a smartphone with an additional Headphone AMP like the Fiio A3, would that solve the potential micro usb power issues? Use low "volume" output from the phone and then adjust the volume to headphones via the headphone AMP.

I would love to simply test all these things and report back but unfortunately none of these items are in stock where I live so everything has to be ordered and shipped (and then returned if necessary) so I'm trying to minimize my what I order to test.

Thanks for all the help too