In reality, there are four kinds of sound cards. On a scale from sucks to far too much; integrated ones, far-off-brand ones, standard ones (generally SoundBlaster), and studio ones. The reason for getting a separate sound card is their onboard RAM and dedicated processor, so anything beyond that is just how much fancy you want on it. Though discontinued, my SoundBlaster Audigy 2 ZS (I believe it was later rebadged into the X-Fi line) has served me well. I'll keep using it until OSes outrun the drivers or PCI is phased out, whichever comes first.
I prefer using headsets with separate plugs for voice and sound. I always find the sound to be a little clearer, plus you don't have the problem figuring out which USB port will utilize it best.
USB headsets generally have their own "sound card" in them which either bypasses or neuters your computer's sound card. They're generally a bad idea in terms of gaming.