Beast Buy is clearing out their Hercules Game Theater XP Audio Station for $75.50 w/ free shipping.
The Vortex 2 sound cards were great sound cards for their time. I tried my MX300 under Win2k but it wasn't fully functional since unfortunately Aureal died before the drivers were finished. It was time to upgrade.
I have both the SB Audigy and Turtle Beach Santa Cruz and think they are both good.
Sound Blaster Audigy
Turtle Beach Santa Cruz
uses the same Cirrus Logic SoundFusion CS4630
soundchip as the Hercules Game Theater XP.
The Hercules Fortissimo uses the Cirrus Logic CS4624
The Audigy has the best EAX implementation and is a bit more forward looking (EAX Advanced, firewire).
Turtle Beach has solid WinXP drivers. A lot of people like it since it has a nice clear sound.
links of interest: http://www.3dss.com/