hardware modem vs. winmodem

A good soundcard will have a DSP chip that carries out the work. A low-quality soundcard will offload the work to the CPU and bog down the system. Even cards with a good DSP will have the CPU doing something.

The time when the difference will be most noticeable is when using positional multichannel audio (like in games). A crappy soundcard will cause a significant speed hit. One thing to keep in mind is that a DS3D (Direct Sound 3D) compatible card can slow down the system, because the DS3D standard allows the sound card to push the work onto the CPU.

As stated above, Creative uses the EMU10K1 and 10K2. Cirrus Logic makes a pretty good DSP that's used in the Hercules GameTheater XP, Turtle Beach Santa Cruz, and VideoLogic Sonic Fury. I think Phillips uses their own DSP with good results.

Lots of computer audio info at the link.