On most speakers, a $35 sound card is supposed to sound the same as a $100 card. In fact, unless you have a bad motherboard, your integrated sound is probably fine.
I got an Asus Xonar DG and had a very noticeable improvement in sound quality, but I have nice speakers and the integrated audio on my old motherboard is terrible. So it's unlikely everyone will have an improvement.
What's your motherboard?