Sound cards are worth investment just for the improvement in audio quality.
I use a creative Z sound card, it provides power for my 880dt.
It really depends in your interests.
About the Creatives Z, I had gotten them at around release time. They do work as advertised.
The scout mode is handy for Counter:strike GO.
The 600 ohm amps powers my beyer 880dts very well...
The sound is excellent.