Yes this is a top of the line headset with a great amp..
OK, So you got a "Top of the Line"headset and amp...Now you want a "Cheap sound card"?
I doubt that a "Cheap" sound card will be audibly better than the on board sound of your motherboard.
If you want a sound card, by all means get one. Just be sure to get one that will make an AUDIBLE difference, or you are just throwing money away.